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authorRyusuke Konishi <konishi.ryusuke@gmail.com>2023-03-28 02:53:18 +0900
committerAndrew Morton <akpm@linux-foundation.org>2023-04-05 18:06:23 -0700
commit6be49d100c22ffea3287a4b19d7639d259888e33 (patch)
tree35e5d1ecfeae22c45788f93ebdd4bb61d949bbfa /fs/nilfs2
parent618a8a917dbf5830e2064d2fa0568940eb5d2584 (diff)
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nilfs2: fix potential UAF of struct nilfs_sc_info in nilfs_segctor_thread()
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@gmail.com Reported-by: syzbot+b08ebcc22f8f3e6be43a@syzkaller.appspotmail.com Link: https://lkml.kernel.org/r/00000000000000660d05f7dfa877@google.com Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/nilfs2')
-rw-r--r--fs/nilfs2/segment.c3
1 files changed, 1 insertions, 2 deletions
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 19446a8243d7..6ad41390fa74 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2609,11 +2609,10 @@ static int nilfs_segctor_thread(void *arg)
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;
}