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]>
Signed-off-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Lino Sanfilippo <[email protected]>
---
drivers/char/tpm/tpm-chip.c | 48 ++++++++-----------------------------
drivers/char/tpm/tpm.h | 1 +
drivers/char/tpm/tpm2-space.c | 55 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 66 insertions(+), 38 deletions(-)
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index ddaeceb..ae6e414 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;
@@ -352,39 +343,20 @@ 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;
if (!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) {
- 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 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;
+
+del_cdev:
+ cdev_device_del(&chip->cdev, &chip->dev);
return rc;
}
@@ -640,8 +610,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
hwrng_unregister(&chip->hwrng);
tpm_bios_log_teardown(chip);
- if (chip->flags & TPM_CHIP_FLAG_TPM2)
+ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
cdev_device_del(&chip->cdevs, &chip->devs);
+ put_device(&chip->devs);
+ }
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 947d1db..ac4b2dc 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -238,6 +238,7 @@ 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_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 784b8b3..6d17f77 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -571,3 +571,58 @@ 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);
+}
+
+/*
+ * 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 out_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 out_put_devs;
+ }
+
+ return 0;
+
+out_put_devs:
+ put_device(&chip->devs);
+
+ return rc;
+}
--
2.7.4
On Thu, Feb 18, 2021 at 09:29:41PM +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]>
> Signed-off-by: Jason Gunthorpe <[email protected]>
> Signed-off-by: Lino Sanfilippo <[email protected]>
> ---
> drivers/char/tpm/tpm-chip.c | 48 ++++++++-----------------------------
> drivers/char/tpm/tpm.h | 1 +
> drivers/char/tpm/tpm2-space.c | 55 +++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 66 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index ddaeceb..ae6e414 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;
> @@ -352,39 +343,20 @@ 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;
>
> if (!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) {
> - 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 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;
> +
> +del_cdev:
> + cdev_device_del(&chip->cdev, &chip->dev);
> return rc;
> }
>
> @@ -640,8 +610,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> hwrng_unregister(&chip->hwrng);
> tpm_bios_log_teardown(chip);
> - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> + if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> cdev_device_del(&chip->cdevs, &chip->devs);
> + put_device(&chip->devs);
> + }
> 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 947d1db..ac4b2dc 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -238,6 +238,7 @@ 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_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 784b8b3..6d17f77 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -571,3 +571,58 @@ 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);
> +}
> +
> +/*
> + * 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 out_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 out_put_devs;
> + }
> +
> + return 0;
> +
> +out_put_devs:
A nit:
1. You have already del_cdev:
2. Here you use a differing convention with out prefix.
I'd suggest that you put err_ to both:
1. err_del_cdev
2. err_put_devs
It's quite coherent what we have already:
linux-tpmdd on next took 8s
❯ git grep "^err_.*" drivers/char/tpm/ | wc -l
17
> + put_device(&chip->devs);
> +
> + return rc;
> +}
> --
> 2.7.4
>
Other than that, no complains.
/Jarkko
On Fri, Feb 19, 2021 at 11:13:45AM +0200, Jarkko Sakkinen wrote:
> On Thu, Feb 18, 2021 at 09:29:41PM +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]>
> > Signed-off-by: Jason Gunthorpe <[email protected]>
> > Signed-off-by: Lino Sanfilippo <[email protected]>
> > ---
> > drivers/char/tpm/tpm-chip.c | 48 ++++++++-----------------------------
> > drivers/char/tpm/tpm.h | 1 +
> > drivers/char/tpm/tpm2-space.c | 55 +++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 66 insertions(+), 38 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index ddaeceb..ae6e414 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;
> > @@ -352,39 +343,20 @@ 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;
> >
> > if (!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) {
> > - 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 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;
> > +
> > +del_cdev:
> > + cdev_device_del(&chip->cdev, &chip->dev);
> > return rc;
> > }
> >
> > @@ -640,8 +610,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> > if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> > hwrng_unregister(&chip->hwrng);
> > tpm_bios_log_teardown(chip);
> > - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > + if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > cdev_device_del(&chip->cdevs, &chip->devs);
> > + put_device(&chip->devs);
> > + }
> > 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 947d1db..ac4b2dc 100644
> > --- a/drivers/char/tpm/tpm.h
> > +++ b/drivers/char/tpm/tpm.h
> > @@ -238,6 +238,7 @@ 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_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 784b8b3..6d17f77 100644
> > --- a/drivers/char/tpm/tpm2-space.c
> > +++ b/drivers/char/tpm/tpm2-space.c
> > @@ -571,3 +571,58 @@ 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);
> > +}
> > +
> > +/*
> > + * 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 out_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 out_put_devs;
> > + }
> > +
> > + return 0;
> > +
> > +out_put_devs:
>
> A nit:
>
> 1. You have already del_cdev:
> 2. Here you use a differing convention with out prefix.
>
> I'd suggest that you put err_ to both:
>
> 1. err_del_cdev
> 2. err_put_devs
>
> It's quite coherent what we have already:
>
> linux-tpmdd on next took 8s
> ❯ git grep "^err_.*" drivers/char/tpm/ | wc -l
> 17
I guess there's some ambiguity with this, but IMHO makes a lot of
sense for code blocks *only* executed as an exception handler.
/Jarkko
Hi,
On 19.02.21 at 10:13, Jarkko Sakkinen wrote:
>> + 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 out_put_devs;
>> + }
>> +
>> + return 0;
>> +
>> +out_put_devs:
>
> A nit:
>
> 1. You have already del_cdev:
> 2. Here you use a differing convention with out prefix.
>
> I'd suggest that you put err_ to both:
>
> 1. err_del_cdev
> 2. err_put_devs
>
> It's quite coherent what we have already:
>
> linux-tpmdd on next took 8s
> ❯ git grep "^err_.*" drivers/char/tpm/ | wc -l
> 17
>
The label del_cdev is indeed a bit inconsistent with the rest of the code.
But AFAICS out_put_devs is not:
1. all labels in tpm2-space.c start with out_
2. there are more hits for out_ across the whole TPM code (i.e. with the same command
you used above I get 31 hits for _out) than for err_.
I suggest to rename del_cdev to something like out_del_cdev or maybe out_cdev which
seems to be even closer to the existing naming scheme for labels.
Regards,
Lino
On Sun, Feb 21, 2021 at 11:19:28AM +0100, Lino Sanfilippo wrote:
>
> Hi,
>
> On 19.02.21 at 10:13, Jarkko Sakkinen wrote:
>
> >> + 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 out_put_devs;
> >> + }
> >> +
> >> + return 0;
> >> +
> >> +out_put_devs:
> >
> > A nit:
> >
> > 1. You have already del_cdev:
> > 2. Here you use a differing convention with out prefix.
> >
> > I'd suggest that you put err_ to both:
> >
> > 1. err_del_cdev
> > 2. err_put_devs
> >
> > It's quite coherent what we have already:
> >
> > linux-tpmdd on next took 8s
> > ❯ git grep "^err_.*" drivers/char/tpm/ | wc -l
> > 17
> >
>
>
> The label del_cdev is indeed a bit inconsistent with the rest of the code.
> But AFAICS out_put_devs is not:
> 1. all labels in tpm2-space.c start with out_
> 2. there are more hits for out_ across the whole TPM code (i.e. with the same command
> you used above I get 31 hits for _out) than for err_.
>
> I suggest to rename del_cdev to something like out_del_cdev or maybe out_cdev which
> seems to be even closer to the existing naming scheme for labels.
OK, that makes sense, thanks!
> Regards,
> Lino
/Jarkko
On Sun, Feb 21, 2021 at 11:19:28AM +0100, Lino Sanfilippo wrote:
>
> Hi,
>
> On 19.02.21 at 10:13, Jarkko Sakkinen wrote:
>
> >> + 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 out_put_devs;
> >> + }
> >> +
> >> + return 0;
> >> +
> >> +out_put_devs:
> >
> > A nit:
> >
> > 1. You have already del_cdev:
> > 2. Here you use a differing convention with out prefix.
> >
> > I'd suggest that you put err_ to both:
> >
> > 1. err_del_cdev
> > 2. err_put_devs
> >
> > It's quite coherent what we have already:
> >
> > linux-tpmdd on next took 8s
> > ❯ git grep "^err_.*" drivers/char/tpm/ | wc -l
> > 17
> >
>
>
> The label del_cdev is indeed a bit inconsistent with the rest of the code.
> But AFAICS out_put_devs is not:
> 1. all labels in tpm2-space.c start with out_
> 2. there are more hits for out_ across the whole TPM code (i.e. with the same command
> you used above I get 31 hits for _out) than for err_.
>
> I suggest to rename del_cdev to something like out_del_cdev or maybe out_cdev which
> seems to be even closer to the existing naming scheme for labels.
Generally, I'd prefer the following pattern:
out: /* out for success path if needed */
return 0;
err_foo:
err_bar:
return ret;
Existing naming scheme is not something to hang into, and I don't care
to preserve it.
> Regards,
> Lino
/Jarkko