2021-12-31 17:21:55

by Hangyu Hua

Subject: [PATCH v4 0/2] usb: gadget: use after free in dev_config

There are two bugs:
dev->buf does not need to be released if it already exists before
executing dev_config.
dev->config and dev->hs_config and dev->dev need to be cleaned if
dev_config fails to avoid UAF.

v2:
1. break one patch up into two separate patches.
2. use "fail:" to clear all members.

v3:
fix a mistake in [PATCH v3 2/2]

v4:
avoid multiple unnecessary statement labels in [PATCH v4 2/2]

Hangyu Hua (2):
usb: gadget: don't release an existing dev->buf
usb: gadget: clear related members when goto fail

drivers/usb/gadget/legacy/inode.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--
2.25.1

2021-12-31 17:21:59

by Hangyu Hua

Subject: [PATCH v4 1/2] usb: gadget: don't release an existing dev->buf

dev->buf does not need to be released if it already exists before
executing dev_config.

Signed-off-by: Hangyu Hua <[email protected]>
---
drivers/usb/gadget/legacy/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index 3b58f4fc0a80..eaad03c0252f 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1826,8 +1826,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
spin_lock_irq (&dev->lock);
value = -EINVAL;
if (dev->buf) {
+ spin_unlock_irq(&dev->lock);
kfree(kbuf);
- goto fail;
+ return value;
}
dev->buf = kbuf;

--
2.25.1

2021-12-31 17:22:03

by Hangyu Hua

Subject: [PATCH v4 2/2] usb: gadget: clear related members when goto fail

dev->config and dev->hs_config and dev->dev need to be cleaned if
dev_config fails to avoid UAF.

Signed-off-by: Hangyu Hua <[email protected]>
---
drivers/usb/gadget/legacy/inode.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index eaad03c0252f..25c8809e0a38 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1875,8 +1875,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)

value = usb_gadget_probe_driver(&gadgetfs_driver);
if (value != 0) {
- kfree (dev->buf);
- dev->buf = NULL;
+ spin_lock_irq(&dev->lock);
+ goto fail;
} else {
/* at this point "good" hardware has for the first time
* let the USB the host see us. alternatively, if users
@@ -1893,6 +1893,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
return value;

fail:
+ dev->config = NULL;
+ dev->hs_config = NULL;
+ dev->dev = NULL;
spin_unlock_irq (&dev->lock);
pr_debug ("%s: %s fail %zd, %p\n", shortname, __func__, value, dev);
kfree (dev->buf);
--
2.25.1

2021-12-31 17:34:49

by Alan Stern

Subject: Re: [PATCH v4 1/2] usb: gadget: don't release an existing dev->buf

On Sat, Jan 01, 2022 at 01:21:37AM +0800, Hangyu Hua wrote:
> dev->buf does not need to be released if it already exists before
> executing dev_config.
>
> Signed-off-by: Hangyu Hua <[email protected]>
> ---

Acked-by: Alan Stern <[email protected]>

> drivers/usb/gadget/legacy/inode.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
> index 3b58f4fc0a80..eaad03c0252f 100644
> --- a/drivers/usb/gadget/legacy/inode.c
> +++ b/drivers/usb/gadget/legacy/inode.c
> @@ -1826,8 +1826,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
> spin_lock_irq (&dev->lock);
> value = -EINVAL;
> if (dev->buf) {
> + spin_unlock_irq(&dev->lock);
> kfree(kbuf);
> - goto fail;
> + return value;
> }
> dev->buf = kbuf;
>
> --
> 2.25.1
>

2021-12-31 17:35:06

by Alan Stern

Subject: Re: [PATCH v4 2/2] usb: gadget: clear related members when goto fail

On Sat, Jan 01, 2022 at 01:21:38AM +0800, Hangyu Hua wrote:
> dev->config and dev->hs_config and dev->dev need to be cleaned if
> dev_config fails to avoid UAF.
>
> Signed-off-by: Hangyu Hua <[email protected]>
> ---

Acked-by: Alan Stern <[email protected]>

> drivers/usb/gadget/legacy/inode.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
> index eaad03c0252f..25c8809e0a38 100644
> --- a/drivers/usb/gadget/legacy/inode.c
> +++ b/drivers/usb/gadget/legacy/inode.c
> @@ -1875,8 +1875,8 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
>
> value = usb_gadget_probe_driver(&gadgetfs_driver);
> if (value != 0) {
> - kfree (dev->buf);
> - dev->buf = NULL;
> + spin_lock_irq(&dev->lock);
> + goto fail;
> } else {
> /* at this point "good" hardware has for the first time
> * let the USB the host see us. alternatively, if users
> @@ -1893,6 +1893,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
> return value;
>
> fail:
> + dev->config = NULL;
> + dev->hs_config = NULL;
> + dev->dev = NULL;
> spin_unlock_irq (&dev->lock);
> pr_debug ("%s: %s fail %zd, %p\n", shortname, __func__, value, dev);
> kfree (dev->buf);
> --
> 2.25.1
>