linux-kernel - [PATCH AUTOSEL 6.6 09/58] ext4: fix i_data_sem unlock order in ext4_ind

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Message-ID: <20241004182503.3672477-9-sashal@kernel.org>
Date: Fri,  4 Oct 2024 14:23:42 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Artem Sadovnikov <ancowi69@...il.com>,
	Ritesh Harjani <ritesh.list@...il.com>,
	Mikhail Ukhin <mish.uxin2012@...dex.ru>,
	Theodore Ts'o <tytso@....edu>,
	Sasha Levin <sashal@...nel.org>,
	adilger.kernel@...ger.ca,
	linux-ext4@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 09/58] ext4: fix i_data_sem unlock order in ext4_ind_migrate()

From: Artem Sadovnikov <ancowi69@...il.com>

[ Upstream commit cc749e61c011c255d81b192a822db650c68b313f ]

Fuzzing reports a possible deadlock in jbd2_log_wait_commit.

This issue is triggered when an EXT4_IOC_MIGRATE ioctl is set to require
synchronous updates because the file descriptor is opened with O_SYNC.
This can lead to the jbd2_journal_stop() function calling
jbd2_might_wait_for_commit(), potentially causing a deadlock if the
EXT4_IOC_MIGRATE call races with a write(2) system call.

This problem only arises when CONFIG_PROVE_LOCKING is enabled. In this
case, the jbd2_might_wait_for_commit macro locks jbd2_handle in the
jbd2_journal_stop function while i_data_sem is locked. This triggers
lockdep because the jbd2_journal_start function might also lock the same
jbd2_handle simultaneously.

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

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
Co-developed-by: Mikhail Ukhin <mish.uxin2012@...dex.ru>
Signed-off-by: Mikhail Ukhin <mish.uxin2012@...dex.ru>
Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>
Rule: add
Link: https://lore.kernel.org/stable/20240404095000.5872-1-mish.uxin2012%40yandex.ru
Link: https://patch.msgid.link/20240829152210.2754-1-ancowi69@gmail.com
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 d98ac2af8199f..a5e1492bbaaa5 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:
 	ext4_writepages_up_write(inode->i_sb, alloc_ctx);
 	return ret;
-- 
2.43.0