In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_fs: initialize reset_work at allocation time
ffs_fs_kill_sb() unconditionally calls cancel_work_sync() on
ffs->reset_work when a functionfs instance is unmounted:
ffs_data_reset(ffs);
cancel_work_sync(&ffs->reset_work);
However ffs->reset_work is only ever initialized via INIT_WORK() in
ffs_func_set_alt() and ffs_func_disable(), and only on the
FFS_DEACTIVATED path. That state is reached solely by ffs_data_closed()
when the instance is mounted with the "no_disconnect" option, so for the
common case (no "no_disconnect", or mounted and unmounted without ever
being deactivated) reset_work is never initialized.
ffs_data_new() allocates the ffs_data with kzalloc_obj() and does not
initialize reset_work, and ffs_data_reset()/ffs_data_clear() do not touch
it either, so reset_work.func is left NULL. cancel_work_sync() on such a
work then trips the WARN_ON(!work->func) guard in __flush_work():
WARNING: kernel/workqueue.c:4301 at __flush_work+0x330/0x360, CPU#3: umount
Call trace:
__flush_work
cancel_work_sync
ffs_fs_kill_sb [usb_f_fs]
deactivate_locked_super
deactivate_super
cleanup_mnt
__cleanup_mnt
task_work_run
exit_to_user_mode_loop
el0_svc
On older kernels cancel_work_sync() on a zero-initialized work struct was
a silent no-op, which hid the missing initialization.
Initialize reset_work once in ffs_data_new() so it is always valid for
the lifetime of the ffs_data, and drop the now-redundant INIT_WORK()
calls from the two deactivation paths.
usb: gadget: f_fs: initialize reset_work at allocation time
ffs_fs_kill_sb() unconditionally calls cancel_work_sync() on
ffs->reset_work when a functionfs instance is unmounted:
ffs_data_reset(ffs);
cancel_work_sync(&ffs->reset_work);
However ffs->reset_work is only ever initialized via INIT_WORK() in
ffs_func_set_alt() and ffs_func_disable(), and only on the
FFS_DEACTIVATED path. That state is reached solely by ffs_data_closed()
when the instance is mounted with the "no_disconnect" option, so for the
common case (no "no_disconnect", or mounted and unmounted without ever
being deactivated) reset_work is never initialized.
ffs_data_new() allocates the ffs_data with kzalloc_obj() and does not
initialize reset_work, and ffs_data_reset()/ffs_data_clear() do not touch
it either, so reset_work.func is left NULL. cancel_work_sync() on such a
work then trips the WARN_ON(!work->func) guard in __flush_work():
WARNING: kernel/workqueue.c:4301 at __flush_work+0x330/0x360, CPU#3: umount
Call trace:
__flush_work
cancel_work_sync
ffs_fs_kill_sb [usb_f_fs]
deactivate_locked_super
deactivate_super
cleanup_mnt
__cleanup_mnt
task_work_run
exit_to_user_mode_loop
el0_svc
On older kernels cancel_work_sync() on a zero-initialized work struct was
a silent no-op, which hid the missing initialization.
Initialize reset_work once in ffs_data_new() so it is always valid for
the lifetime of the ffs_data, and drop the now-redundant INIT_WORK()
calls from the two deactivation paths.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
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| Linux | Linux | affected |
|
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Fixes
Solution
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Workaround
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References
History
Thu, 06 Aug 2026 08:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-476 |
Thu, 06 Aug 2026 07:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: usb: gadget: f_fs: initialize reset_work at allocation time ffs_fs_kill_sb() unconditionally calls cancel_work_sync() on ffs->reset_work when a functionfs instance is unmounted: ffs_data_reset(ffs); cancel_work_sync(&ffs->reset_work); However ffs->reset_work is only ever initialized via INIT_WORK() in ffs_func_set_alt() and ffs_func_disable(), and only on the FFS_DEACTIVATED path. That state is reached solely by ffs_data_closed() when the instance is mounted with the "no_disconnect" option, so for the common case (no "no_disconnect", or mounted and unmounted without ever being deactivated) reset_work is never initialized. ffs_data_new() allocates the ffs_data with kzalloc_obj() and does not initialize reset_work, and ffs_data_reset()/ffs_data_clear() do not touch it either, so reset_work.func is left NULL. cancel_work_sync() on such a work then trips the WARN_ON(!work->func) guard in __flush_work(): WARNING: kernel/workqueue.c:4301 at __flush_work+0x330/0x360, CPU#3: umount Call trace: __flush_work cancel_work_sync ffs_fs_kill_sb [usb_f_fs] deactivate_locked_super deactivate_super cleanup_mnt __cleanup_mnt task_work_run exit_to_user_mode_loop el0_svc On older kernels cancel_work_sync() on a zero-initialized work struct was a silent no-op, which hid the missing initialization. Initialize reset_work once in ffs_data_new() so it is always valid for the lifetime of the ffs_data, and drop the now-redundant INIT_WORK() calls from the two deactivation paths. | |
| Title | usb: gadget: f_fs: initialize reset_work at allocation time | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-08-06T07:13:50.309Z
Reserved: 2026-07-19T15:36:31.799Z
Link: CVE-2026-64594
Vulnrichment
No data.
NVD
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Redhat
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OpenCVE Enrichment
Updated: 2026-08-06T11:00:06Z
Weaknesses