From 3d32aaa7e66d5c1479a3c31d6c2c5d45dd0d3b89 Mon Sep 17 00:00:00 2001

From: Mike Snitzer <snitzer@kernel.org>

Date: Mon, 17 Apr 2023 11:59:56 -0400

Subject: [PATCH] dm ioctl: fix nested locking in table_clear() to remove

 deadlock concern

Git-commit: 3d32aaa7e66d5c1479a3c31d6c2c5d45dd0d3b89

Patch-mainline: v6.4-rc1

References: bsc#1210806

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@vger.kernel.org

Reported-by: Zheng Zhang <zheng.zhang@email.ucr.edu>

Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Signed-off-by: Coly Li <colyli@suse.de>

---

 drivers/md/dm-ioctl.c | 7 ++++---

 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c

index 50a1259294d1..7d5c9c582ed2 100644

--- a/drivers/md/dm-ioctl.c

+++ b/drivers/md/dm-ioctl.c

@@ -1556,11 +1556,12 @@ static int table_clear(struct file *filp, struct dm_ioctl *param, size_t param_s

 		has_new_map = true;

 	}

-	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);

-- 

2.35.3