From: Jan Kara <jack@suse.cz>
To: syzbot <syzbot+7f4a27091759e2fe7453@syzkaller.appspotmail.com>
Cc: jack@suse.com, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
tytso@mit.edu
Subject: Re: KASAN: use-after-free Write in jbd2_log_do_checkpoint
Date: Thu, 4 Oct 2018 12:27:46 +0200 [thread overview]
Message-ID: <20181004102746.GF11529@quack2.suse.cz> (raw)
In-Reply-To: <0000000000002be16c05760f576d@google.com>
On Mon 17-09-18 04:19:02, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 2e2a0c961a87 Merge branch 'progarray_mapinmap_dump'
> git tree: bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17622811400000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8f59875069d721b6
> dashboard link: https://syzkaller.appspot.com/bug?extid=7f4a27091759e2fe7453
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7f4a27091759e2fe7453@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: use-after-free in atomic_inc
> include/asm-generic/atomic-instrumented.h:109 [inline]
> BUG: KASAN: use-after-free in get_bh include/linux/buffer_head.h:283
> [inline]
> BUG: KASAN: use-after-free in jbd2_log_do_checkpoint+0x113d/0x13e0
> fs/jbd2/checkpoint.c:337
> Write of size 4 at addr ffff8801b6d96300 by task syz-executor1/904
This is at:
if (buffer_locked(bh)) {
spin_unlock(&journal->j_list_lock);
get_bh(bh);
wait_on_buffer(bh);
/* the journal_head may have gone by now */
BUFFER_TRACE(bh, "brelse");
__brelse(bh);
spin_lock(&journal->j_list_lock);
goto restart2;
}
And indeed that get_bh() should be called before we unlock j_list_lock as
otherwise we can race with jbd2_journal_try_to_free_buffers(). I'll send a
fix.
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
prev parent reply other threads:[~2018-10-04 17:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-17 11:19 KASAN: use-after-free Write in jbd2_log_do_checkpoint syzbot
2018-10-04 10:27 ` Jan Kara [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=20181004102746.GF11529@quack2.suse.cz \
--to=jack@suse.cz \
--cc=jack@suse.com \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=syzbot+7f4a27091759e2fe7453@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tytso@mit.edu \
/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).