[SRU][X][PATCH v2 1/1] ext4: fix i_data_sem unlock order in ext4_ind_migrate()

[Alice C. Munduruca]

From: Artem Sadovnikov <ancowi69 at gmail.com>

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 at gmail.com>
Co-developed-by: Mikhail Ukhin <mish.uxin2012 at yandex.ru>
Signed-off-by: Mikhail Ukhin <mish.uxin2012 at yandex.ru>
Signed-off-by: Artem Sadovnikov <ancowi69 at gmail.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 at mit.edu>
(backported from commit cc749e61c011c255d81b192a822db650c68b313f)
[cremfuelled: Ignore `out_unlock`, since the commit it was introduced
 is not present]
CVE-2024-50006
Signed-off-by: Alice C. Munduruca <alice.munduruca at canonical.com>
---
 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 a4651894cc33..1b2696192eba 100644
--- a/fs/ext4/migrate.c
+++ b/fs/ext4/migrate.c
@@ -674,7 +674,7 @@ int ext4_ind_migrate(struct inode *inode)
 		ei->i_data[i] = cpu_to_le32(blk++);
 	ext4_mark_inode_dirty(handle, inode);
 errout:
-	ext4_journal_stop(handle);
 	up_write(&EXT4_I(inode)->i_data_sem);
+	ext4_journal_stop(handle);
 	return ret;
 }
-- 
2.48.1