From e99abe6190ac31166d67e840248268c603177524 Mon Sep 17 00:00:00 2001 From: Xiaxi Shen Date: Mon, 4 Nov 2024 10:38:43 +0800 Subject: [PATCH] ext4: fix timer use-after-free on failed mount mainline inclusion from mainline-v6.12-rc1 commit 0ce160c5bdb67081a62293028dc85758a8efb22a category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAYRD8 CVE: CVE-2024-49960 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0ce160c5bdb67081a62293028dc85758a8efb22a -------------------------------- Syzbot has found an ODEBUG bug in ext4_fill_super The del_timer_sync function cancels the s_err_report timer, which reminds about filesystem errors daily. We should guarantee the timer is no longer active before kfree(sbi). When filesystem mounting fails, the flow goes to failed_mount3, where an error occurs when ext4_stop_mmpd is called, causing a read I/O failure. This triggers the ext4_handle_error function that ultimately re-arms the timer, leaving the s_err_report timer active before kfree(sbi) is called. Fix the issue by canceling the s_err_report timer after calling ext4_stop_mmpd. Signed-off-by: Xiaxi Shen Reported-and-tested-by: syzbot+59e0101c430934bc9a36@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=59e0101c430934bc9a36 Link: https://patch.msgid.link/20240715043336.98097-1-shenxiaxi26@gmail.com Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Conflicts: fs/ext4/super.c [Context differences.] Signed-off-by: Yongjian Sun --- fs/ext4/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index fecbf5c2de3f..c389416934c1 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5277,8 +5277,8 @@ failed_mount8: __maybe_unused failed_mount3: /* flush s_error_work before sbi destroy */ flush_work(&sbi->s_error_work); - del_timer_sync(&sbi->s_err_report); ext4_stop_mmpd(sbi); + del_timer_sync(&sbi->s_err_report); failed_mount2: rcu_read_lock(); group_desc = rcu_dereference(sbi->s_group_desc); -- Gitee