Bug 2419841 (CVE-2025-40315)

Summary: CVE-2025-40315 kernel: usb: gadget: f_fs: Fix epfile null pointer access after ep enable
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-12-08 07:02:39 UTC 
In the Linux kernel, the following vulnerability has been resolved:

usb: gadget: f_fs: Fix epfile null pointer access after ep enable.

A race condition occurs when ffs_func_eps_enable() runs concurrently
with ffs_data_reset(). The ffs_data_clear() called in ffs_data_reset()
sets ffs->epfiles to NULL before resetting ffs->eps_count to 0, leading
to a NULL pointer dereference when accessing epfile->ep in
ffs_func_eps_enable() after successful usb_ep_enable().

The ffs->epfiles pointer is set to NULL in both ffs_data_clear() and
ffs_data_close() functions, and its modification is protected by the
spinlock ffs->eps_lock. And the whole ffs_func_eps_enable() function
is also protected by ffs->eps_lock.

Thus, add NULL pointer handling for ffs->epfiles in the
ffs_func_eps_enable() function to fix issues
Comment 1 Alexander B 2025-12-10 10:55:57 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120822-CVE-2025-40315-38da@gregkh/T