The patch titled
Subject: nilfs2: fix potential UAF of struct nilfs_sc_info in nilfs_segctor_thread()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
nilfs2-fix-potential-uaf-of-struct-nilfs_sc_info-in-nilfs_segctor_thread.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-potential-uaf-of-struct-nilfs_sc_info-in-nilfs_segctor_thread.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Subject: nilfs2: fix potential UAF of struct nilfs_sc_info in nilfs_segctor_thread()
Date: Tue, 28 Mar 2023 02:53:18 +0900
The finalization of nilfs_segctor_thread() can race with
nilfs_segctor_kill_thread() which terminates that thread, potentially
causing a use-after-free BUG as KASAN detected.
At the end of nilfs_segctor_thread(), it assigns NULL to "sc_task" member
of "struct nilfs_sc_info" to indicate the thread has finished, and then
notifies nilfs_segctor_kill_thread() of this using waitqueue
"sc_wait_task" on the struct nilfs_sc_info.
However, here, immediately after the NULL assignment to "sc_task", it is
possible that nilfs_segctor_kill_thread() will detect it and return to
continue the deallocation, freeing the nilfs_sc_info structure before the
thread does the notification.
This fixes the issue by protecting the NULL assignment to "sc_task" and
its notification, with spinlock "sc_state_lock" of the struct
nilfs_sc_info. Since nilfs_segctor_kill_thread() does a final check to
see if "sc_task" is NULL with "sc_state_lock" locked, this can eliminate
the race.
Link: https://lkml.kernel.org/r/20230327175318.8060-1-konishi.ryusuke@xxxxxxxxx
Reported-by: syzbot+b08ebcc22f8f3e6be43a@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/00000000000000660d05f7dfa877@xxxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/segment.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/fs/nilfs2/segment.c~nilfs2-fix-potential-uaf-of-struct-nilfs_sc_info-in-nilfs_segctor_thread
+++ a/fs/nilfs2/segment.c
@@ -2609,11 +2609,10 @@ static int nilfs_segctor_thread(void *ar
goto loop;
end_thread:
- spin_unlock(&sci->sc_state_lock);
-
/* end sync. */
sci->sc_task = NULL;
wake_up(&sci->sc_wait_task); /* for nilfs_segctor_kill_thread() */
+ spin_unlock(&sci->sc_state_lock);
return 0;
}
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-potential-uaf-of-struct-nilfs_sc_info-in-nilfs_segctor_thread.patch
