ksmbd: fix use-after-free by using call_rcu() for oplock_info

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commit 1dfd062caa upstream.

ksmbd currently frees oplock_info immediately using kfree(), even
though it is accessed under RCU read-side critical sections in places
like opinfo_get() and proc_show_files().

Since there is no RCU grace period delay between nullifying the pointer
and freeing the memory, a reader can still access oplock_info
structure after it has been freed. This can leads to a use-after-free
especially in opinfo_get() where atomic_inc_not_zero() is called on
already freed memory.

Fix this by switching to deferred freeing using call_rcu().

Fixes: 18b4fac5ef ("ksmbd: fix use-after-free in smb_break_all_levII_oplock()")
Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Namjae Jeon 2026-03-07 11:32:31 +09:00 • committed by Greg Kroah-Hartman

parent 8f5b1a7cb0

commit 1d6abf1456

2 changed files with 24 additions and 10 deletions

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29

fs/smb/server/oplock.c

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5

fs/smb/server/oplock.h

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