From: Xiaxi Shen Date: Mon, 15 Jul 2024 04:33:36 +0000 (-0700) Subject: ext4: fix timer use-after-free on failed mount X-Git-Tag: v6.12-rc1~117^2~83 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0ce160c5bdb67081a62293028dc85758a8efb22a;p=thirdparty%2Fkernel%2Flinux.git ext4: fix timer use-after-free on failed mount 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 We should guarantee the timer is no longer active before kfree(sbi).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 --- diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 7806044ed8162..99ecd4ac7be00 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5621,8 +5621,8 @@ failed_mount3a: failed_mount3: /* flush s_sb_upd_work before sbi destroy */ flush_work(&sbi->s_sb_upd_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)