linux-ext4 - [PATCH v2] ext4: fix i_data_sem unlock order in ext4_ind

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Date: Sat,  6 Apr 2024 00:08:03 +0300
From: Mikhail Ukhin <mish.uxin2012@...dex.ru>
To: "Theodore Ts'o" <tytso@....edu>
Cc: Mikhail Ukhin <mish.uxin2012@...dex.ru>,
	stable@...r.kernel.org,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Michail Ivanov <iwanov-23@...ru>,
	Pavel Koshutin <koshutin.pavel@...dex.ru>,
	lvc-project@...uxtesting.org,
	Ritesh Harjani <ritesh.list@...il.com>,
	Artem Sadovnikov <ancowi69@...il.com>
Subject: [PATCH v2] ext4: fix i_data_sem unlock order in ext4_ind_migrate()

Fuzzing reports a possible deadlock in jbd2_log_wait_commit.

The problem occurs in ext4_ind_migrate due to an incorrect order of
unlocking of the journal and write semaphores - the order of unlocking
must be the reverse of the order of locking.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>
Signed-off-by: Mikhail Ukhin <mish.uxin2012@...dex.ru>
---
 v2: New addresses have been added and Ritesh Harjani has been noted as a
 reviewer.
 fs/ext4/migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
index b0ea646454ac..59290356aa5b 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -663,8 +663,8 @@ int ext4_ind_migrate(struct inode *inode)
 	if (unlikely(ret2 && !ret))
 		ret = ret2;
 errout:
-	ext4_journal_stop(handle);
 	up_write(&EXT4_I(inode)->i_data_sem);
+	ext4_journal_stop(handle);
 out_unlock:
 	percpu_up_write(&sbi->s_writepages_rwsem);
 	return ret;
-- 
2.25.1