From d584a79eea72d4454c084acd55d26deccb0367cb Mon Sep 17 00:00:00 2001 From: Xiaxi Shen <shenxiaxi26@gmail.com> Date: Sun, 14 Jul 2024 21:33:36 -0700 Subject: [PATCH] ext4: fix timer use-after-free on failed mount commit 0ce160c5bdb67081a62293028dc85758a8efb22a upstream. 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 We should guarantee the timer is no longer active before kfree(sbi).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 <shenxiaxi26@gmail.com> 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 <tytso@mit.edu> Cc: stable@kernel.org Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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 3bf214d4afef5..987d49e18dbe8 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5617,8 +5617,8 @@ failed_mount9: __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); ext4_group_desc_free(sbi); failed_mount: if (sbi->s_chksum_driver) -- GitLab