Description

In the Linux kernel, the following vulnerability has been resolved: usb: f_fs: Fix use-after-free for epfile Consider a case where ffs_func_eps_disable is called from ffs_func_disable as part of composition switch and at the same time ffs_epfile_release get called from userspace. ffs_epfile_release will free up the read buffer and call ffs_data_closed which in turn destroys ffs->epfiles and mark it as NULL. While this was happening the driver has already initialized the local epfile in ffs_func_eps_disable which is now freed and waiting to acquire the spinlock. Once spinlock is acquired the driver proceeds with the stale value of epfile and tries to free the already freed read buffer causing use-after-free. Following is the illustration of the race: CPU1 CPU2 ffs_func_eps_disable epfiles (local copy) ffs_epfile_release ffs_data_closed if (last file closed) ffs_data_reset ffs_data_clear ffs_epfiles_destroy spin_lock dereference epfiles Fix this races by taking epfiles local copy & assigning it under spinlock and if epfiles(local) is null then update it in ffs->epfiles then finally destroy it. Extending the scope further from the race, protecting the ep related structures, and concurrent accesses.

Metrics

 

CVSS Version 4.0 CVSS Version 3.x CVSS Version 2.0

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CVSS 4.0 Severity and Vector Strings:

NIST: NVD

N/A

NVD assessment not yet provided.

CVSS 3.x Severity and Vector Strings:

NIST: NVD

Base Score:  N/A

NVD assessment not yet provided.

CVSS 2.0 Severity and Vector Strings:

NIST: NVD

Base Score: N/A

NVD assessment not yet provided.

In the Linux kernel, the following vulnerability has been resolved:

usb: f_fs: Fix use-after-free for epfile

Consider a case where ffs_func_eps_disable is called from
ffs_func_disable as part of composition switch and at the
same time ffs_epfile_release get called from userspace.
ffs_epfile_release will free up the read buffer and call
ffs_data_closed which in turn destroys ffs->epfiles and
mark it as NULL. While this was happening the driver has
already initialized the local epfile in ffs_fun

kernel.org https://git.kernel.org/stable/c/0042178a69eb77a979e36a50dcce9794a3140ef8 [No types assigned]

kernel.org https://git.kernel.org/stable/c/32048f4be071f9a6966744243f1786f45bb22dc2 [No types assigned]

kernel.org https://git.kernel.org/stable/c/3e078b18753669615301d946297bafd69294ad2c [No types assigned]

kernel.org https://git.kernel.org/stable/c/72a8aee863af099d4434314c4536d6c9a61dcf3c [No types assigned]

kernel.org https://git.kernel.org/stable/c/c9fc422c9a43e3d58d246334a71f3390401781dc [No types assigned]

kernel.org https://git.kernel.org/stable/c/cfe5f6fd335d882bcc829a1c8a7d462a455c626e [No types assigned]

kernel.org https://git.kernel.org/stable/c/ebe2b1add1055b903e2acd86b290a85297edc0b3 [No types assigned]