From: "Theodore Y. Ts'o" <tytso@mit.edu>
To: syzbot <syzbot+a2872d6feea6918008a9@syzkaller.appspotmail.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk,
linux-ext4@vger.kernel.org
Subject: Re: KASAN: use-after-free Read in seq_escape
Date: Tue, 2 Oct 2018 10:49:33 -0400 [thread overview]
Message-ID: <20181002144933.GC17537@thunk.org> (raw)
In-Reply-To: <000000000000902cb10577255369@google.com>
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@mit.edu>
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@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
---
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
prev parent reply other threads:[~2018-10-02 21:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-01 6:58 KASAN: use-after-free Read in seq_escape syzbot
2018-10-02 14:49 ` Theodore Y. Ts'o [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181002144933.GC17537@thunk.org \
--to=tytso@mit.edu \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=syzbot+a2872d6feea6918008a9@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).