This is a note to let you know that I've just added the patch titled
dm ioctl: fix nested locking in table_clear() to remove deadlock concern
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dm-ioctl-fix-nested-locking-in-table_clear-to-remove-deadlock-concern.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3d32aaa7e66d5c1479a3c31d6c2c5d45dd0d3b89 Mon Sep 17 00:00:00 2001
From: Mike Snitzer <snitzer@xxxxxxxxxx>
Date: Mon, 17 Apr 2023 11:59:56 -0400
Subject: dm ioctl: fix nested locking in table_clear() to remove deadlock concern
From: Mike Snitzer <snitzer@xxxxxxxxxx>
commit 3d32aaa7e66d5c1479a3c31d6c2c5d45dd0d3b89 upstream.
syzkaller found the following problematic rwsem locking (with write
lock already held):
down_read+0x9d/0x450 kernel/locking/rwsem.c:1509
dm_get_inactive_table+0x2b/0xc0 drivers/md/dm-ioctl.c:773
__dev_status+0x4fd/0x7c0 drivers/md/dm-ioctl.c:844
table_clear+0x197/0x280 drivers/md/dm-ioctl.c:1537
In table_clear, it first acquires a write lock
https://elixir.bootlin.com/linux/v6.2/source/drivers/md/dm-ioctl.c#L1520
down_write(&_hash_lock);
Then before the lock is released at L1539, there is a path shown above:
table_clear -> __dev_status -> dm_get_inactive_table -> down_read
https://elixir.bootlin.com/linux/v6.2/source/drivers/md/dm-ioctl.c#L773
down_read(&_hash_lock);
It tries to acquire the same read lock again, resulting in the deadlock
problem.
Fix this by moving table_clear()'s __dev_status() call to after its
up_write(&_hash_lock);
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Zheng Zhang <zheng.zhang@xxxxxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-ioctl.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1410,11 +1410,12 @@ static int table_clear(struct file *filp
hc->new_map = NULL;
}
- param->flags &= ~DM_INACTIVE_PRESENT_FLAG;
-
- __dev_status(hc->md, param);
md = hc->md;
up_write(&_hash_lock);
+
+ param->flags &= ~DM_INACTIVE_PRESENT_FLAG;
+ __dev_status(md, param);
+
if (old_map) {
dm_sync_table(md);
dm_table_destroy(old_map);
Patches currently in stable-queue which might be from snitzer@xxxxxxxxxx are
queue-4.19/dm-flakey-fix-a-crash-with-invalid-table-line.patch
queue-4.19/dm-ioctl-fix-nested-locking-in-table_clear-to-remove-deadlock-concern.patch
queue-4.19/dm-verity-fix-error-handling-for-check_at_most_once-on-fec.patch
queue-4.19/dm-integrity-call-kmem_cache_destroy-in-dm_integrity_init-error-path.patch
