From cc749e61c011c255d81b192a822db650c68b313f Mon Sep 17 00:00:00 2001 From: Artem Sadovnikov <ancowi69@gmail.com> Date: Thu, 29 Aug 2024 15:22:09 +0000 Subject: [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate() 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@gmail.com> Co-developed-by: Mikhail Ukhin <mish.uxin2012@yandex.ru> Signed-off-by: Mikhail Ukhin <mish.uxin2012@yandex.ru> Signed-off-by: Artem Sadovnikov <ancowi69@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@mit.edu> --- 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 0f68b8a14560e..1b0dfd963d3f0 100644 --- a/fs/ext4/migrate.c +++ b/fs/ext4/migrate.c @@ -664,8 +664,8 @@ 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; -- GitLab