module/dups: Fix use-after-free in kmod_dup_req lifetime handling

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The kmod dups code uses RCU to ensure that a kmod_dup_req instance is freed
only after it is no longer referenced. When releasing an instance, the
kmod_dup_request_delete() function removes the kmod_dup_req from the
dup_kmod_reqs list, waits via synchronize_rcu() and finally frees it.
However, this doesn't work correctly because parallel users referencing the
instance in kmod_dup_request_exists_wait() don't enter an RCU read-side
critical section. This can result in a use-after-free.

The kmod_dup_request_exists_wait() function may need to hold a valid
reference to a kmod_dup_req instance across a blocking wait until the
corresponding modprobe command completes. This makes it unsuitable for RCU.

Fix the issue by changing the lifecycle management of kmod_dup_req to use
reference counting.

Fixes: 8660484ed1 ("module: add debugging auto-load duplicate module support")
Reviewed-by: Aaron Tomlin <atomlin@atomlin.com>
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>

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This commit is contained in:

Petr Pavlu 2026-08-06 11:10:16 +02:00

parent d258ed8a86

commit 5eecb11b54

1 changed files with 40 additions and 16 deletions

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kernel/module/dups.c

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