LinuxLists.cc - [PATCH v9 0/1] This patch fixes a reference count issue in the TPM core code

2022-03-02 12:39:03

Subject: [PATCH v9 0/1] This patch fixes a reference count issue in the TPM core code

Changes in v9:
- add a function tpm_devs_remove() as counterpart to tpm_devs_add()
as suggested by Jason

Changes in v8:
- adjust names of jump labels for
as requested by Jarkko

Changes in v7:
- adjust naming of jump labels to fit better the used label naming scheme

Changes in v6:
- rename function tpm2_add_device() to tpm_devs_add() as requested by Jarko
- add function descriptions
- fix source code formatting

Changes in v5:
- move function tpm_add_tpm2_char_device() to tpm2-space.c and rename
it to tpm2_add_device() as requested by Jarko
- put "cc" tag before all other tags
- ensure that the error path in tpm2_add_device() always calls
the release() function of chip->devs as requested by Jason
- reformat a code line as suggested by David Laight

Changes in v4:
- drop patch 2 (tpm: in tpm2_del_space check if ops pointer is still
valid) since James Bottomley offered a cleaner solution for this
- reimplement patch 1 to setup the /dev/tpmrm device only in case of TPM2
and avoid the installation of another action handler. This is based on a
suggestion and basic implementation done by Jason Gunthorpe.
- added tag to CC stable

Changes in v3:
- drop the patch that introduces the new function tpm_chip_free()
- rework the commit messages for the patches (style, typos, etc.)
- add fixes tag to patch 2
- add James Bottomley to cc list
- add stable mailing list to cc list

Changes in v2:
- drop the patch that erroneously cleaned up after failed installation of
an action handler in tpmm_chip_alloc() (pointed out by Jarkko Sakkinen)
- make the commit message for patch 1 more detailed
- add fixes tags and kernel logs

Lino Sanfilippo (1):
tpm: fix reference counting for struct tpm_chip

drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
drivers/char/tpm/tpm.h | 2 ++
drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
3 files changed, 75 insertions(+), 38 deletions(-)

base-commit: c8db90d3e723086a54be83e0a2b108146c57e0de
--
2.35.1

2022-03-02 23:10:56

by Lino Sanfilippo

[permalink] [raw]

Subject: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

From: Lino Sanfilippo <[email protected]>

The following sequence of operations results in a refcount warning:

1. Open device /dev/tpmrm.
2. Remove module tpm_tis_spi.
3. Write a TPM command to the file descriptor opened at step 1.

------------[ cut here ]------------
WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
refcount_t: addition on 0; use-after-free.
Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
Hardware name: BCM2711
[<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
[<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
[<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
[<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
[<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
[<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
[<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
[<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
[<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
[<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
Exception stack(0xc226bfa8 to 0xc226bff0)
bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
bfe0: 0000006c beafe648 0001056c b6eb6944
---[ end trace d4b8409def9b8b1f ]---

The reason for this warning is the attempt to get the chip->dev reference
in tpm_common_write() although the reference counter is already zero.

Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
extra reference used to prevent a premature zero counter is never taken,
because the required TPM_CHIP_FLAG_TPM2 flag is never set.

Fix this by moving the TPM 2 character device handling from
tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
in time when the flag has been set in case of TPM2.

Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
already introduced function tpm_devs_release() to release the extra
reference but did not implement the required put on chip->devs that results
in the call of this function.

Fix this by putting chip->devs in tpm_chip_unregister().

Finally move the new implementation for the TPM 2 handling into a new
function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
good case and error cases.

Cc: [email protected]
Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
Co-developed-by: Jason Gunthorpe <[email protected]>
Tested-by: Stefan Berger <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Lino Sanfilippo <[email protected]>
---
drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
drivers/char/tpm/tpm.h | 2 ++
drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
3 files changed, 75 insertions(+), 38 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index b009e7479b70..783d65fc71f0 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev)
kfree(chip);
}

-static void tpm_devs_release(struct device *dev)
-{
- struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
-
- /* release the master device reference */
- put_device(&chip->dev);
-}
-
/**
* tpm_class_shutdown() - prepare the TPM device for loss of power.
* @dev: device to which the chip is associated.
@@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
chip->dev_num = rc;

device_initialize(&chip->dev);
- device_initialize(&chip->devs);

chip->dev.class = tpm_class;
chip->dev.class->shutdown_pre = tpm_class_shutdown;
@@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
chip->dev.parent = pdev;
chip->dev.groups = chip->groups;

- chip->devs.parent = pdev;
- chip->devs.class = tpmrm_class;
- chip->devs.release = tpm_devs_release;
- /* get extra reference on main device to hold on
- * behalf of devs. This holds the chip structure
- * while cdevs is in use. The corresponding put
- * is in the tpm_devs_release (TPM2 only)
- */
- if (chip->flags & TPM_CHIP_FLAG_TPM2)
- get_device(&chip->dev);
-
if (chip->dev_num == 0)
chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
else
chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

- chip->devs.devt =
- MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
-
rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
- if (rc)
- goto out;
- rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
if (rc)
goto out;

@@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
chip->flags |= TPM_CHIP_FLAG_VIRTUAL;

cdev_init(&chip->cdev, &tpm_fops);
- cdev_init(&chip->cdevs, &tpmrm_fops);
chip->cdev.owner = THIS_MODULE;
- chip->cdevs.owner = THIS_MODULE;

rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
if (rc) {
@@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
return chip;

out:
- put_device(&chip->devs);
put_device(&chip->dev);
return ERR_PTR(rc);
}
@@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tpm_chip *chip)
}

if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
- rc = cdev_device_add(&chip->cdevs, &chip->devs);
- if (rc) {
- dev_err(&chip->devs,
- "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
- dev_name(&chip->devs), MAJOR(chip->devs.devt),
- MINOR(chip->devs.devt), rc);
- return rc;
- }
+ rc = tpm_devs_add(chip);
+ if (rc)
+ goto err_del_cdev;
}

/* Make the chip available. */
@@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tpm_chip *chip)
idr_replace(&dev_nums_idr, chip, chip->dev_num);
mutex_unlock(&idr_lock);

+ return 0;
+
+err_del_cdev:
+ cdev_device_del(&chip->cdev, &chip->dev);
return rc;
}

@@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
hwrng_unregister(&chip->hwrng);
tpm_bios_log_teardown(chip);
if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
- cdev_device_del(&chip->cdevs, &chip->devs);
+ tpm_devs_remove(chip);
tpm_del_char_device(chip);
}
EXPORT_SYMBOL_GPL(tpm_chip_unregister);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 283f78211c3a..2163c6ee0d36 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
size_t cmdsiz);
int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
size_t *bufsiz);
+int tpm_devs_add(struct tpm_chip *chip);
+void tpm_devs_remove(struct tpm_chip *chip);

void tpm_bios_log_setup(struct tpm_chip *chip);
void tpm_bios_log_teardown(struct tpm_chip *chip);
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 97e916856cf3..265ec72b1d81 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
return rc;
}
+
+/*
+ * Put the reference to the main device.
+ */
+static void tpm_devs_release(struct device *dev)
+{
+ struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
+
+ /* release the master device reference */
+ put_device(&chip->dev);
+}
+
+/*
+ * Remove the device file for exposed TPM spaces and release the device
+ * reference. This may also release the reference to the master device.
+ */
+void tpm_devs_remove(struct tpm_chip *chip)
+{
+ cdev_device_del(&chip->cdevs, &chip->devs);
+ put_device(&chip->devs);
+}
+
+/*
+ * Add a device file to expose TPM spaces. Also take a reference to the
+ * main device.
+ */
+int tpm_devs_add(struct tpm_chip *chip)
+{
+ int rc;
+
+ device_initialize(&chip->devs);
+ chip->devs.parent = chip->dev.parent;
+ chip->devs.class = tpmrm_class;
+
+ /*
+ * Get extra reference on main device to hold on behalf of devs.
+ * This holds the chip structure while cdevs is in use. The
+ * corresponding put is in the tpm_devs_release.
+ */
+ get_device(&chip->dev);
+ chip->devs.release = tpm_devs_release;
+ chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
+ cdev_init(&chip->cdevs, &tpmrm_fops);
+ chip->cdevs.owner = THIS_MODULE;
+
+ rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
+ if (rc)
+ goto err_put_devs;
+
+ rc = cdev_device_add(&chip->cdevs, &chip->devs);
+ if (rc) {
+ dev_err(&chip->devs,
+ "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
+ dev_name(&chip->devs), MAJOR(chip->devs.devt),
+ MINOR(chip->devs.devt), rc);
+ goto err_put_devs;
+ }
+
+ return 0;
+
+err_put_devs:
+ put_device(&chip->devs);
+
+ return rc;
+}
--
2.35.1

2022-03-04 02:41:56

by Jarkko Sakkinen

[permalink] [raw]

Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <[email protected]>
>
> The following sequence of operations results in a refcount warning:
>
> 1. Open device /dev/tpmrm.
> 2. Remove module tpm_tis_spi.
> 3. Write a TPM command to the file descriptor opened at step 1.
>
> ------------[ cut here ]------------
> WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
> refcount_t: addition on 0; use-after-free.
> Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
> sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
> brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
> raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
> snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
> CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
> Hardware name: BCM2711
> [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
> [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
> [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
> [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
> [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
> [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
> [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
> [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
> [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
> [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
> Exception stack(0xc226bfa8 to 0xc226bff0)
> bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
> bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
> bfe0: 0000006c beafe648 0001056c b6eb6944
> ---[ end trace d4b8409def9b8b1f ]---
>
> The reason for this warning is the attempt to get the chip->dev reference
> in tpm_common_write() although the reference counter is already zero.
>
> Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
> extra reference used to prevent a premature zero counter is never taken,
> because the required TPM_CHIP_FLAG_TPM2 flag is never set.
>
> Fix this by moving the TPM 2 character device handling from
> tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
> in time when the flag has been set in case of TPM2.
>
> Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> already introduced function tpm_devs_release() to release the extra
> reference but did not implement the required put on chip->devs that results
> in the call of this function.
>
> Fix this by putting chip->devs in tpm_chip_unregister().
>
> Finally move the new implementation for the TPM 2 handling into a new
> function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
> good case and error cases.
>
> Cc: [email protected]
> Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
> Co-developed-by: Jason Gunthorpe <[email protected]>
> Tested-by: Stefan Berger <[email protected]>
> Signed-off-by: Jason Gunthorpe <[email protected]>
> Signed-off-by: Lino Sanfilippo <[email protected]>
> ---
> drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
> drivers/char/tpm/tpm.h | 2 ++
> drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
> 3 files changed, 75 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index b009e7479b70..783d65fc71f0 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev)
> kfree(chip);
> }
>
> -static void tpm_devs_release(struct device *dev)
> -{
> - struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> -
> - /* release the master device reference */
> - put_device(&chip->dev);
> -}
> -
> /**
> * tpm_class_shutdown() - prepare the TPM device for loss of power.
> * @dev: device to which the chip is associated.
> @@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> chip->dev_num = rc;
>
> device_initialize(&chip->dev);
> - device_initialize(&chip->devs);
>
> chip->dev.class = tpm_class;
> chip->dev.class->shutdown_pre = tpm_class_shutdown;
> @@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> chip->dev.parent = pdev;
> chip->dev.groups = chip->groups;
>
> - chip->devs.parent = pdev;
> - chip->devs.class = tpmrm_class;
> - chip->devs.release = tpm_devs_release;
> - /* get extra reference on main device to hold on
> - * behalf of devs. This holds the chip structure
> - * while cdevs is in use. The corresponding put
> - * is in the tpm_devs_release (TPM2 only)
> - */
> - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> - get_device(&chip->dev);
> -
> if (chip->dev_num == 0)
> chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
> else
> chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);
>
> - chip->devs.devt =
> - MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> -
> rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
> - if (rc)
> - goto out;
> - rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> if (rc)
> goto out;
>
> @@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> chip->flags |= TPM_CHIP_FLAG_VIRTUAL;
>
> cdev_init(&chip->cdev, &tpm_fops);
> - cdev_init(&chip->cdevs, &tpmrm_fops);
> chip->cdev.owner = THIS_MODULE;
> - chip->cdevs.owner = THIS_MODULE;
>
> rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
> if (rc) {
> @@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> return chip;
>
> out:
> - put_device(&chip->devs);
> put_device(&chip->dev);
> return ERR_PTR(rc);
> }
> @@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> }
>
> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
> - rc = cdev_device_add(&chip->cdevs, &chip->devs);
> - if (rc) {
> - dev_err(&chip->devs,
> - "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> - dev_name(&chip->devs), MAJOR(chip->devs.devt),
> - MINOR(chip->devs.devt), rc);
> - return rc;
> - }
> + rc = tpm_devs_add(chip);
> + if (rc)
> + goto err_del_cdev;
> }
>
> /* Make the chip available. */
> @@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> idr_replace(&dev_nums_idr, chip, chip->dev_num);
> mutex_unlock(&idr_lock);
>
> + return 0;
> +
> +err_del_cdev:
> + cdev_device_del(&chip->cdev, &chip->dev);
> return rc;
> }
>
> @@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> hwrng_unregister(&chip->hwrng);
> tpm_bios_log_teardown(chip);
> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
> - cdev_device_del(&chip->cdevs, &chip->devs);
> + tpm_devs_remove(chip);
> tpm_del_char_device(chip);
> }
> EXPORT_SYMBOL_GPL(tpm_chip_unregister);
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 283f78211c3a..2163c6ee0d36 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> size_t cmdsiz);
> int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
> size_t *bufsiz);
> +int tpm_devs_add(struct tpm_chip *chip);
> +void tpm_devs_remove(struct tpm_chip *chip);
>
> void tpm_bios_log_setup(struct tpm_chip *chip);
> void tpm_bios_log_teardown(struct tpm_chip *chip);
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 97e916856cf3..265ec72b1d81 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
> return rc;
> }
> +
> +/*
> + * Put the reference to the main device.
> + */
> +static void tpm_devs_release(struct device *dev)
> +{
> + struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> +
> + /* release the master device reference */
> + put_device(&chip->dev);
> +}
> +
> +/*
> + * Remove the device file for exposed TPM spaces and release the device
> + * reference. This may also release the reference to the master device.
> + */
> +void tpm_devs_remove(struct tpm_chip *chip)
> +{
> + cdev_device_del(&chip->cdevs, &chip->devs);
> + put_device(&chip->devs);
> +}
> +
> +/*
> + * Add a device file to expose TPM spaces. Also take a reference to the
> + * main device.
> + */
> +int tpm_devs_add(struct tpm_chip *chip)
> +{
> + int rc;
> +
> + device_initialize(&chip->devs);
> + chip->devs.parent = chip->dev.parent;
> + chip->devs.class = tpmrm_class;
> +
> + /*
> + * Get extra reference on main device to hold on behalf of devs.
> + * This holds the chip structure while cdevs is in use. The
> + * corresponding put is in the tpm_devs_release.
> + */
> + get_device(&chip->dev);
> + chip->devs.release = tpm_devs_release;
> + chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> + cdev_init(&chip->cdevs, &tpmrm_fops);
> + chip->cdevs.owner = THIS_MODULE;
> +
> + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> + if (rc)
> + goto err_put_devs;
> +
> + rc = cdev_device_add(&chip->cdevs, &chip->devs);
> + if (rc) {
> + dev_err(&chip->devs,
> + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> + dev_name(&chip->devs), MAJOR(chip->devs.devt),
> + MINOR(chip->devs.devt), rc);
> + goto err_put_devs;
> + }
> +
> + return 0;
> +
> +err_put_devs:
> + put_device(&chip->devs);
> +
> + return rc;
> +}
> --
> 2.35.1
>

LGTM, thank you.

Reviewed-by: Jarkko Sakkinen <[email protected]>

Stefan, if possible, for sanity check, redo test with v9.

BR, Jarkko

2022-03-04 19:48:13

by Jason Gunthorpe

[permalink] [raw]

Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

2022-03-04 20:31:42

by Stefan Berger

[permalink] [raw]

Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

On 3/3/22 17:45, Jarkko Sakkinen wrote:
> On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <[email protected]>
>>
>> The following sequence of operations results in a refcount warning:
>>
>> 1. Open device /dev/tpmrm.
>> 2. Remove module tpm_tis_spi.
>> 3. Write a TPM command to the file descriptor opened at step 1.
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
>> refcount_t: addition on 0; use-after-free.
>> Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
>> sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
>> brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
>> raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
>> snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
>> CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
>> Hardware name: BCM2711
>> [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
>> [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
>> [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
>> [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
>> [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
>> [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
>> [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
>> [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
>> [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
>> [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
>> Exception stack(0xc226bfa8 to 0xc226bff0)
>> bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
>> bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
>> bfe0: 0000006c beafe648 0001056c b6eb6944
>> ---[ end trace d4b8409def9b8b1f ]---
>>
>> The reason for this warning is the attempt to get the chip->dev reference
>> in tpm_common_write() although the reference counter is already zero.
>>
>> Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
>> extra reference used to prevent a premature zero counter is never taken,
>> because the required TPM_CHIP_FLAG_TPM2 flag is never set.
>>
>> Fix this by moving the TPM 2 character device handling from
>> tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
>> in time when the flag has been set in case of TPM2.
>>
>> Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
>> already introduced function tpm_devs_release() to release the extra
>> reference but did not implement the required put on chip->devs that results
>> in the call of this function.
>>
>> Fix this by putting chip->devs in tpm_chip_unregister().
>>
>> Finally move the new implementation for the TPM 2 handling into a new
>> function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
>> good case and error cases.
>>
>> Cc: [email protected]
>> Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
>> Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
>> Co-developed-by: Jason Gunthorpe <[email protected]>
>> Tested-by: Stefan Berger <[email protected]>
>> Signed-off-by: Jason Gunthorpe <[email protected]>
>> Signed-off-by: Lino Sanfilippo <[email protected]>
>> ---
>> drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
>> drivers/char/tpm/tpm.h | 2 ++
>> drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
>> 3 files changed, 75 insertions(+), 38 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
>> index b009e7479b70..783d65fc71f0 100644
>> --- a/drivers/char/tpm/tpm-chip.c
>> +++ b/drivers/char/tpm/tpm-chip.c
>> @@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev)
>> kfree(chip);
>> }
>>
>> -static void tpm_devs_release(struct device *dev)
>> -{
>> - struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
>> -
>> - /* release the master device reference */
>> - put_device(&chip->dev);
>> -}
>> -
>> /**
>> * tpm_class_shutdown() - prepare the TPM device for loss of power.
>> * @dev: device to which the chip is associated.
>> @@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>> chip->dev_num = rc;
>>
>> device_initialize(&chip->dev);
>> - device_initialize(&chip->devs);
>>
>> chip->dev.class = tpm_class;
>> chip->dev.class->shutdown_pre = tpm_class_shutdown;
>> @@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>> chip->dev.parent = pdev;
>> chip->dev.groups = chip->groups;
>>
>> - chip->devs.parent = pdev;
>> - chip->devs.class = tpmrm_class;
>> - chip->devs.release = tpm_devs_release;
>> - /* get extra reference on main device to hold on
>> - * behalf of devs. This holds the chip structure
>> - * while cdevs is in use. The corresponding put
>> - * is in the tpm_devs_release (TPM2 only)
>> - */
>> - if (chip->flags & TPM_CHIP_FLAG_TPM2)
>> - get_device(&chip->dev);
>> -
>> if (chip->dev_num == 0)
>> chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
>> else
>> chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);
>>
>> - chip->devs.devt =
>> - MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
>> -
>> rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
>> - if (rc)
>> - goto out;
>> - rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
>> if (rc)
>> goto out;
>>
>> @@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>> chip->flags |= TPM_CHIP_FLAG_VIRTUAL;
>>
>> cdev_init(&chip->cdev, &tpm_fops);
>> - cdev_init(&chip->cdevs, &tpmrm_fops);
>> chip->cdev.owner = THIS_MODULE;
>> - chip->cdevs.owner = THIS_MODULE;
>>
>> rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
>> if (rc) {
>> @@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>> return chip;
>>
>> out:
>> - put_device(&chip->devs);
>> put_device(&chip->dev);
>> return ERR_PTR(rc);
>> }
>> @@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tpm_chip *chip)
>> }
>>
>> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
>> - rc = cdev_device_add(&chip->cdevs, &chip->devs);
>> - if (rc) {
>> - dev_err(&chip->devs,
>> - "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
>> - dev_name(&chip->devs), MAJOR(chip->devs.devt),
>> - MINOR(chip->devs.devt), rc);
>> - return rc;
>> - }
>> + rc = tpm_devs_add(chip);
>> + if (rc)
>> + goto err_del_cdev;
>> }
>>
>> /* Make the chip available. */
>> @@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tpm_chip *chip)
>> idr_replace(&dev_nums_idr, chip, chip->dev_num);
>> mutex_unlock(&idr_lock);
>>
>> + return 0;
>> +
>> +err_del_cdev:
>> + cdev_device_del(&chip->cdev, &chip->dev);
>> return rc;
>> }
>>
>> @@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>> hwrng_unregister(&chip->hwrng);
>> tpm_bios_log_teardown(chip);
>> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
>> - cdev_device_del(&chip->cdevs, &chip->devs);
>> + tpm_devs_remove(chip);
>> tpm_del_char_device(chip);
>> }
>> EXPORT_SYMBOL_GPL(tpm_chip_unregister);
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index 283f78211c3a..2163c6ee0d36 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
>> size_t cmdsiz);
>> int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
>> size_t *bufsiz);
>> +int tpm_devs_add(struct tpm_chip *chip);
>> +void tpm_devs_remove(struct tpm_chip *chip);
>>
>> void tpm_bios_log_setup(struct tpm_chip *chip);
>> void tpm_bios_log_teardown(struct tpm_chip *chip);
>> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
>> index 97e916856cf3..265ec72b1d81 100644
>> --- a/drivers/char/tpm/tpm2-space.c
>> +++ b/drivers/char/tpm/tpm2-space.c
>> @@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
>> dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
>> return rc;
>> }
>> +
>> +/*
>> + * Put the reference to the main device.
>> + */
>> +static void tpm_devs_release(struct device *dev)
>> +{
>> + struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
>> +
>> + /* release the master device reference */
>> + put_device(&chip->dev);
>> +}
>> +
>> +/*
>> + * Remove the device file for exposed TPM spaces and release the device
>> + * reference. This may also release the reference to the master device.
>> + */
>> +void tpm_devs_remove(struct tpm_chip *chip)
>> +{
>> + cdev_device_del(&chip->cdevs, &chip->devs);
>> + put_device(&chip->devs);
>> +}
>> +
>> +/*
>> + * Add a device file to expose TPM spaces. Also take a reference to the
>> + * main device.
>> + */
>> +int tpm_devs_add(struct tpm_chip *chip)
>> +{
>> + int rc;
>> +
>> + device_initialize(&chip->devs);
>> + chip->devs.parent = chip->dev.parent;
>> + chip->devs.class = tpmrm_class;
>> +
>> + /*
>> + * Get extra reference on main device to hold on behalf of devs.
>> + * This holds the chip structure while cdevs is in use. The
>> + * corresponding put is in the tpm_devs_release.
>> + */
>> + get_device(&chip->dev);
>> + chip->devs.release = tpm_devs_release;
>> + chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
>> + cdev_init(&chip->cdevs, &tpmrm_fops);
>> + chip->cdevs.owner = THIS_MODULE;
>> +
>> + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
>> + if (rc)
>> + goto err_put_devs;
>> +
>> + rc = cdev_device_add(&chip->cdevs, &chip->devs);
>> + if (rc) {
>> + dev_err(&chip->devs,
>> + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
>> + dev_name(&chip->devs), MAJOR(chip->devs.devt),
>> + MINOR(chip->devs.devt), rc);
>> + goto err_put_devs;
>> + }
>> +
>> + return 0;
>> +
>> +err_put_devs:
>> + put_device(&chip->devs);
>> +
>> + return rc;
>> +}
>> --
>> 2.35.1
>>
> LGTM, thank you.
>
> Reviewed-by: Jarkko Sakkinen <[email protected]>
>
> Stefan, if possible, for sanity check, redo test with v9.

We need that other patch as well!

Tested-by: Stefan Berger <[email protected]>

Stefan

>
> BR, Jarkko

2022-03-05 06:48:05

by Jarkko Sakkinen

[permalink] [raw]

Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

On Sat, Mar 05, 2022 at 07:21:26AM +0200, Jarkko Sakkinen wrote:
> On Fri, Mar 04, 2022 at 01:34:06PM -0500, Stefan Berger wrote:
> >
> > On 3/3/22 17:45, Jarkko Sakkinen wrote:
> > > On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote:
> > > > From: Lino Sanfilippo <[email protected]>
> > > >
> > > > The following sequence of operations results in a refcount warning:
> > > >
> > > > 1. Open device /dev/tpmrm.
> > > > 2. Remove module tpm_tis_spi.
> > > > 3. Write a TPM command to the file descriptor opened at step 1.
> > > >
> > > > ------------[ cut here ]------------
> > > > WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
> > > > refcount_t: addition on 0; use-after-free.
> > > > Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
> > > > sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
> > > > brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
> > > > raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
> > > > snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
> > > > CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
> > > > Hardware name: BCM2711
> > > > [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
> > > > [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
> > > > [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
> > > > [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
> > > > [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
> > > > [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
> > > > [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
> > > > [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
> > > > [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
> > > > [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
> > > > Exception stack(0xc226bfa8 to 0xc226bff0)
> > > > bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
> > > > bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
> > > > bfe0: 0000006c beafe648 0001056c b6eb6944
> > > > ---[ end trace d4b8409def9b8b1f ]---
> > > >
> > > > The reason for this warning is the attempt to get the chip->dev reference
> > > > in tpm_common_write() although the reference counter is already zero.
> > > >
> > > > Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
> > > > extra reference used to prevent a premature zero counter is never taken,
> > > > because the required TPM_CHIP_FLAG_TPM2 flag is never set.
> > > >
> > > > Fix this by moving the TPM 2 character device handling from
> > > > tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
> > > > in time when the flag has been set in case of TPM2.
> > > >
> > > > Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> > > > already introduced function tpm_devs_release() to release the extra
> > > > reference but did not implement the required put on chip->devs that results
> > > > in the call of this function.
> > > >
> > > > Fix this by putting chip->devs in tpm_chip_unregister().
> > > >
> > > > Finally move the new implementation for the TPM 2 handling into a new
> > > > function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
> > > > good case and error cases.
> > > >
> > > > Cc: [email protected]
> > > > Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> > > > Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
> > > > Co-developed-by: Jason Gunthorpe <[email protected]>
> > > > Tested-by: Stefan Berger <[email protected]>
> > > > Signed-off-by: Jason Gunthorpe <[email protected]>
> > > > Signed-off-by: Lino Sanfilippo <[email protected]>
> > > > ---
> > > > drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
> > > > drivers/char/tpm/tpm.h | 2 ++
> > > > drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
> > > > 3 files changed, 75 insertions(+), 38 deletions(-)
> > > >
> > > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > > index b009e7479b70..783d65fc71f0 100644
> > > > --- a/drivers/char/tpm/tpm-chip.c
> > > > +++ b/drivers/char/tpm/tpm-chip.c
> > > > @@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev)
> > > > kfree(chip);
> > > > }
> > > > -static void tpm_devs_release(struct device *dev)
> > > > -{
> > > > - struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> > > > -
> > > > - /* release the master device reference */
> > > > - put_device(&chip->dev);
> > > > -}
> > > > -
> > > > /**
> > > > * tpm_class_shutdown() - prepare the TPM device for loss of power.
> > > > * @dev: device to which the chip is associated.
> > > > @@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > > chip->dev_num = rc;
> > > > device_initialize(&chip->dev);
> > > > - device_initialize(&chip->devs);
> > > > chip->dev.class = tpm_class;
> > > > chip->dev.class->shutdown_pre = tpm_class_shutdown;
> > > > @@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > > chip->dev.parent = pdev;
> > > > chip->dev.groups = chip->groups;
> > > > - chip->devs.parent = pdev;
> > > > - chip->devs.class = tpmrm_class;
> > > > - chip->devs.release = tpm_devs_release;
> > > > - /* get extra reference on main device to hold on
> > > > - * behalf of devs. This holds the chip structure
> > > > - * while cdevs is in use. The corresponding put
> > > > - * is in the tpm_devs_release (TPM2 only)
> > > > - */
> > > > - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > > > - get_device(&chip->dev);
> > > > -
> > > > if (chip->dev_num == 0)
> > > > chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
> > > > else
> > > > chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);
> > > > - chip->devs.devt =
> > > > - MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> > > > -
> > > > rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
> > > > - if (rc)
> > > > - goto out;
> > > > - rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > > if (rc)
> > > > goto out;
> > > > @@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > > chip->flags |= TPM_CHIP_FLAG_VIRTUAL;
> > > > cdev_init(&chip->cdev, &tpm_fops);
> > > > - cdev_init(&chip->cdevs, &tpmrm_fops);
> > > > chip->cdev.owner = THIS_MODULE;
> > > > - chip->cdevs.owner = THIS_MODULE;
> > > > rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
> > > > if (rc) {
> > > > @@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > > return chip;
> > > > out:
> > > > - put_device(&chip->devs);
> > > > put_device(&chip->dev);
> > > > return ERR_PTR(rc);
> > > > }
> > > > @@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> > > > }
> > > > if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
> > > > - rc = cdev_device_add(&chip->cdevs, &chip->devs);
> > > > - if (rc) {
> > > > - dev_err(&chip->devs,
> > > > - "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> > > > - dev_name(&chip->devs), MAJOR(chip->devs.devt),
> > > > - MINOR(chip->devs.devt), rc);
> > > > - return rc;
> > > > - }
> > > > + rc = tpm_devs_add(chip);
> > > > + if (rc)
> > > > + goto err_del_cdev;
> > > > }
> > > > /* Make the chip available. */
> > > > @@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> > > > idr_replace(&dev_nums_idr, chip, chip->dev_num);
> > > > mutex_unlock(&idr_lock);
> > > > + return 0;
> > > > +
> > > > +err_del_cdev:
> > > > + cdev_device_del(&chip->cdev, &chip->dev);
> > > > return rc;
> > > > }
> > > > @@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> > > > hwrng_unregister(&chip->hwrng);
> > > > tpm_bios_log_teardown(chip);
> > > > if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
> > > > - cdev_device_del(&chip->cdevs, &chip->devs);
> > > > + tpm_devs_remove(chip);
> > > > tpm_del_char_device(chip);
> > > > }
> > > > EXPORT_SYMBOL_GPL(tpm_chip_unregister);
> > > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > > > index 283f78211c3a..2163c6ee0d36 100644
> > > > --- a/drivers/char/tpm/tpm.h
> > > > +++ b/drivers/char/tpm/tpm.h
> > > > @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> > > > size_t cmdsiz);
> > > > int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
> > > > size_t *bufsiz);
> > > > +int tpm_devs_add(struct tpm_chip *chip);
> > > > +void tpm_devs_remove(struct tpm_chip *chip);
> > > > void tpm_bios_log_setup(struct tpm_chip *chip);
> > > > void tpm_bios_log_teardown(struct tpm_chip *chip);
> > > > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> > > > index 97e916856cf3..265ec72b1d81 100644
> > > > --- a/drivers/char/tpm/tpm2-space.c
> > > > +++ b/drivers/char/tpm/tpm2-space.c
> > > > @@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> > > > dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
> > > > return rc;
> > > > }
> > > > +
> > > > +/*
> > > > + * Put the reference to the main device.
> > > > + */
> > > > +static void tpm_devs_release(struct device *dev)
> > > > +{
> > > > + struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> > > > +
> > > > + /* release the master device reference */
> > > > + put_device(&chip->dev);
> > > > +}
> > > > +
> > > > +/*
> > > > + * Remove the device file for exposed TPM spaces and release the device
> > > > + * reference. This may also release the reference to the master device.
> > > > + */
> > > > +void tpm_devs_remove(struct tpm_chip *chip)
> > > > +{
> > > > + cdev_device_del(&chip->cdevs, &chip->devs);
> > > > + put_device(&chip->devs);
> > > > +}
> > > > +
> > > > +/*
> > > > + * Add a device file to expose TPM spaces. Also take a reference to the
> > > > + * main device.
> > > > + */
> > > > +int tpm_devs_add(struct tpm_chip *chip)
> > > > +{
> > > > + int rc;
> > > > +
> > > > + device_initialize(&chip->devs);
> > > > + chip->devs.parent = chip->dev.parent;
> > > > + chip->devs.class = tpmrm_class;
> > > > +
> > > > + /*
> > > > + * Get extra reference on main device to hold on behalf of devs.
> > > > + * This holds the chip structure while cdevs is in use. The
> > > > + * corresponding put is in the tpm_devs_release.
> > > > + */
> > > > + get_device(&chip->dev);
> > > > + chip->devs.release = tpm_devs_release;
> > > > + chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> > > > + cdev_init(&chip->cdevs, &tpmrm_fops);
> > > > + chip->cdevs.owner = THIS_MODULE;
> > > > +
> > > > + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > > + if (rc)
> > > > + goto err_put_devs;
> > > > +
> > > > + rc = cdev_device_add(&chip->cdevs, &chip->devs);
> > > > + if (rc) {
> > > > + dev_err(&chip->devs,
> > > > + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> > > > + dev_name(&chip->devs), MAJOR(chip->devs.devt),
> > > > + MINOR(chip->devs.devt), rc);
> > > > + goto err_put_devs;
> > > > + }
> > > > +
> > > > + return 0;
> > > > +
> > > > +err_put_devs:
> > > > + put_device(&chip->devs);
> > > > +
> > > > + return rc;
> > > > +}
> > > > --
> > > > 2.35.1
> > > >
> > > LGTM, thank you.
> > >
> > > Reviewed-by: Jarkko Sakkinen <[email protected]>
> > >
> > > Stefan, if possible, for sanity check, redo test with v9.
> >
> > We need that other patch as well!
>
> Yes.
>
> > Tested-by: Stefan Berger <[email protected]>
>
> Thank you.

I fixed this manually:

$ scripts/checkpatch.pl 0001-tpm-fix-reference-counting-for-struct-tpm_chip.patch
WARNING: From:/Signed-off-by: email address mismatch: 'From: Lino Sanfilippo <[email protected]>' != 'Signed-off-by: Lino Sanfilippo <[email protected]>'

Changed "From:" to sob address.

It's now in

git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git

and should appear to linux-next.

BR, Jarkko

2022-03-05 06:53:00

by Jarkko Sakkinen

[permalink] [raw]

Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip

On Fri, Mar 04, 2022 at 01:34:06PM -0500, Stefan Berger wrote:
>
> On 3/3/22 17:45, Jarkko Sakkinen wrote:
> > On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote:
> > > From: Lino Sanfilippo <[email protected]>
> > >
> > > The following sequence of operations results in a refcount warning:
> > >
> > > 1. Open device /dev/tpmrm.
> > > 2. Remove module tpm_tis_spi.
> > > 3. Write a TPM command to the file descriptor opened at step 1.
> > >
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
> > > refcount_t: addition on 0; use-after-free.
> > > Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
> > > sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
> > > brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
> > > raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
> > > snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
> > > CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
> > > Hardware name: BCM2711
> > > [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
> > > [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
> > > [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
> > > [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
> > > [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
> > > [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
> > > [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
> > > [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
> > > [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
> > > [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
> > > Exception stack(0xc226bfa8 to 0xc226bff0)
> > > bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
> > > bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
> > > bfe0: 0000006c beafe648 0001056c b6eb6944
> > > ---[ end trace d4b8409def9b8b1f ]---
> > >
> > > The reason for this warning is the attempt to get the chip->dev reference
> > > in tpm_common_write() although the reference counter is already zero.
> > >
> > > Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
> > > extra reference used to prevent a premature zero counter is never taken,
> > > because the required TPM_CHIP_FLAG_TPM2 flag is never set.
> > >
> > > Fix this by moving the TPM 2 character device handling from
> > > tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
> > > in time when the flag has been set in case of TPM2.
> > >
> > > Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> > > already introduced function tpm_devs_release() to release the extra
> > > reference but did not implement the required put on chip->devs that results
> > > in the call of this function.
> > >
> > > Fix this by putting chip->devs in tpm_chip_unregister().
> > >
> > > Finally move the new implementation for the TPM 2 handling into a new
> > > function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
> > > good case and error cases.
> > >
> > > Cc: [email protected]
> > > Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
> > > Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
> > > Co-developed-by: Jason Gunthorpe <[email protected]>
> > > Tested-by: Stefan Berger <[email protected]>
> > > Signed-off-by: Jason Gunthorpe <[email protected]>
> > > Signed-off-by: Lino Sanfilippo <[email protected]>
> > > ---
> > > drivers/char/tpm/tpm-chip.c | 46 +++++--------------------
> > > drivers/char/tpm/tpm.h | 2 ++
> > > drivers/char/tpm/tpm2-space.c | 65 +++++++++++++++++++++++++++++++++++
> > > 3 files changed, 75 insertions(+), 38 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > index b009e7479b70..783d65fc71f0 100644
> > > --- a/drivers/char/tpm/tpm-chip.c
> > > +++ b/drivers/char/tpm/tpm-chip.c
> > > @@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev)
> > > kfree(chip);
> > > }
> > > -static void tpm_devs_release(struct device *dev)
> > > -{
> > > - struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> > > -
> > > - /* release the master device reference */
> > > - put_device(&chip->dev);
> > > -}
> > > -
> > > /**
> > > * tpm_class_shutdown() - prepare the TPM device for loss of power.
> > > * @dev: device to which the chip is associated.
> > > @@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > chip->dev_num = rc;
> > > device_initialize(&chip->dev);
> > > - device_initialize(&chip->devs);
> > > chip->dev.class = tpm_class;
> > > chip->dev.class->shutdown_pre = tpm_class_shutdown;
> > > @@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > chip->dev.parent = pdev;
> > > chip->dev.groups = chip->groups;
> > > - chip->devs.parent = pdev;
> > > - chip->devs.class = tpmrm_class;
> > > - chip->devs.release = tpm_devs_release;
> > > - /* get extra reference on main device to hold on
> > > - * behalf of devs. This holds the chip structure
> > > - * while cdevs is in use. The corresponding put
> > > - * is in the tpm_devs_release (TPM2 only)
> > > - */
> > > - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > > - get_device(&chip->dev);
> > > -
> > > if (chip->dev_num == 0)
> > > chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
> > > else
> > > chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);
> > > - chip->devs.devt =
> > > - MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> > > -
> > > rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
> > > - if (rc)
> > > - goto out;
> > > - rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > if (rc)
> > > goto out;
> > > @@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > chip->flags |= TPM_CHIP_FLAG_VIRTUAL;
> > > cdev_init(&chip->cdev, &tpm_fops);
> > > - cdev_init(&chip->cdevs, &tpmrm_fops);
> > > chip->cdev.owner = THIS_MODULE;
> > > - chip->cdevs.owner = THIS_MODULE;
> > > rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
> > > if (rc) {
> > > @@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> > > return chip;
> > > out:
> > > - put_device(&chip->devs);
> > > put_device(&chip->dev);
> > > return ERR_PTR(rc);
> > > }
> > > @@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> > > }
> > > if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
> > > - rc = cdev_device_add(&chip->cdevs, &chip->devs);
> > > - if (rc) {
> > > - dev_err(&chip->devs,
> > > - "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> > > - dev_name(&chip->devs), MAJOR(chip->devs.devt),
> > > - MINOR(chip->devs.devt), rc);
> > > - return rc;
> > > - }
> > > + rc = tpm_devs_add(chip);
> > > + if (rc)
> > > + goto err_del_cdev;
> > > }
> > > /* Make the chip available. */
> > > @@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> > > idr_replace(&dev_nums_idr, chip, chip->dev_num);
> > > mutex_unlock(&idr_lock);
> > > + return 0;
> > > +
> > > +err_del_cdev:
> > > + cdev_device_del(&chip->cdev, &chip->dev);
> > > return rc;
> > > }
> > > @@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> > > hwrng_unregister(&chip->hwrng);
> > > tpm_bios_log_teardown(chip);
> > > if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
> > > - cdev_device_del(&chip->cdevs, &chip->devs);
> > > + tpm_devs_remove(chip);
> > > tpm_del_char_device(chip);
> > > }
> > > EXPORT_SYMBOL_GPL(tpm_chip_unregister);
> > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > > index 283f78211c3a..2163c6ee0d36 100644
> > > --- a/drivers/char/tpm/tpm.h
> > > +++ b/drivers/char/tpm/tpm.h
> > > @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> > > size_t cmdsiz);
> > > int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
> > > size_t *bufsiz);
> > > +int tpm_devs_add(struct tpm_chip *chip);
> > > +void tpm_devs_remove(struct tpm_chip *chip);
> > > void tpm_bios_log_setup(struct tpm_chip *chip);
> > > void tpm_bios_log_teardown(struct tpm_chip *chip);
> > > diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> > > index 97e916856cf3..265ec72b1d81 100644
> > > --- a/drivers/char/tpm/tpm2-space.c
> > > +++ b/drivers/char/tpm/tpm2-space.c
> > > @@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> > > dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
> > > return rc;
> > > }
> > > +
> > > +/*
> > > + * Put the reference to the main device.
> > > + */
> > > +static void tpm_devs_release(struct device *dev)
> > > +{
> > > + struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
> > > +
> > > + /* release the master device reference */
> > > + put_device(&chip->dev);
> > > +}
> > > +
> > > +/*
> > > + * Remove the device file for exposed TPM spaces and release the device
> > > + * reference. This may also release the reference to the master device.
> > > + */
> > > +void tpm_devs_remove(struct tpm_chip *chip)
> > > +{
> > > + cdev_device_del(&chip->cdevs, &chip->devs);
> > > + put_device(&chip->devs);
> > > +}
> > > +
> > > +/*
> > > + * Add a device file to expose TPM spaces. Also take a reference to the
> > > + * main device.
> > > + */
> > > +int tpm_devs_add(struct tpm_chip *chip)
> > > +{
> > > + int rc;
> > > +
> > > + device_initialize(&chip->devs);
> > > + chip->devs.parent = chip->dev.parent;
> > > + chip->devs.class = tpmrm_class;
> > > +
> > > + /*
> > > + * Get extra reference on main device to hold on behalf of devs.
> > > + * This holds the chip structure while cdevs is in use. The
> > > + * corresponding put is in the tpm_devs_release.
> > > + */
> > > + get_device(&chip->dev);
> > > + chip->devs.release = tpm_devs_release;
> > > + chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> > > + cdev_init(&chip->cdevs, &tpmrm_fops);
> > > + chip->cdevs.owner = THIS_MODULE;
> > > +
> > > + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > + if (rc)
> > > + goto err_put_devs;
> > > +
> > > + rc = cdev_device_add(&chip->cdevs, &chip->devs);
> > > + if (rc) {
> > > + dev_err(&chip->devs,
> > > + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
> > > + dev_name(&chip->devs), MAJOR(chip->devs.devt),
> > > + MINOR(chip->devs.devt), rc);
> > > + goto err_put_devs;
> > > + }
> > > +
> > > + return 0;
> > > +
> > > +err_put_devs:
> > > + put_device(&chip->devs);
> > > +
> > > + return rc;
> > > +}
> > > --
> > > 2.35.1
> > >
> > LGTM, thank you.
> >
> > Reviewed-by: Jarkko Sakkinen <[email protected]>
> >
> > Stefan, if possible, for sanity check, redo test with v9.
>
> We need that other patch as well!

Yes.

> Tested-by: Stefan Berger <[email protected]>

Thank you.

BR, Jarkko