On Sun, Sep 30, 2018 at 11:58:02PM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: 17b57b1883c1 Linux 4.19-rc6 > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1672d711400000 > kernel config: https://syzkaller.appspot.com/x/.config?x=c0af03fe452b65fb > dashboard link: https://syzkaller.appspot.com/bug?extid=a2872d6feea6918008a9 > compiler: gcc (GCC) 8.0.1 20180413 (experimental) This should be fixed with the following patch. - Ted >From 89cc85e761c5b905b1a61cb85440bf9b5e841c80 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o <tytso@xxxxxxx> Date: Tue, 2 Oct 2018 10:40:57 -0400 Subject: [PATCH] ext4: fix use-after-free race in ext4_remount()'s error path It's possible for ext4_show_quota_options() to try reading s_qf_names[i] while it is being modified by ext4_remount() --- most notably, in ext4_remount's error path when the original values of the quota file name gets restored. Reported-by: syzbot+a2872d6feea6918008a9@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Cc: stable@xxxxxxxxxx --- fs/ext4/super.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index faf293ed8060..11a1bfae0937 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -2048,11 +2048,13 @@ static inline void ext4_show_quota_options(struct seq_file *seq, seq_printf(seq, ",jqfmt=%s", fmtname); } + down_read(&sb->s_umount); if (sbi->s_qf_names[USRQUOTA]) seq_show_option(seq, "usrjquota", sbi->s_qf_names[USRQUOTA]); if (sbi->s_qf_names[GRPQUOTA]) seq_show_option(seq, "grpjquota", sbi->s_qf_names[GRPQUOTA]); + up_read(&sb->s_umount); #endif } -- 2.18.0.rc0
