From: Al Viro <viro@zeniv.linux.org.uk>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Jens Axboe <axboe@kernel.dk>,
syzbot <syzbot+c88a7030da47945a3cc3@syzkaller.appspotmail.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com, io-uring@vger.kernel.org
Subject: Re: [syzbot] WARNING in mntput_no_expire (2)
Date: Sun, 4 Apr 2021 18:50:10 +0000 [thread overview]
Message-ID: <YGoKYktYPA86Qwju@zeniv-ca.linux.org.uk> (raw)
In-Reply-To: <20210404170513.mfl5liccdaxjnpls@wittgenstein>
On Sun, Apr 04, 2021 at 07:05:13PM +0200, Christian Brauner wrote:
> On Sun, Apr 04, 2021 at 04:44:06PM +0000, Al Viro wrote:
> > On Sun, Apr 04, 2021 at 06:40:40PM +0200, Christian Brauner wrote:
> >
> > > > Very interesting. What happens if you call loop() twice? And now I wonder
> > > > whether it's root or cwd, actually... Hmm...
> > > >
> > > > How about this:
> > > > fd = open("/proc/self/mountinfo", 0);
> > > > mkdir("./newroot/foo", 0777);
> > > > mount("./newroot/foo", "./newroot/foo", 0, MS_BIND, NULL);
> > > > chroot("./newroot");
> > > > chdir("/foo");
> > > > while (1) {
> > > > static char buf[4096];
> > > > int n = read(fd, buf, 4096);
> > > > if (n <= 0)
> > > > break;
> > > > write(1, buf, n);
> > > > }
> > > > close(fd);
> > > > drop_caps();
> > > > loop();
> > > > as the end of namespace_sandbox_proc(), instead of
> > > > chroot("./newroot");
> > > > chdir("/");
> > > > drop_caps();
> > > > loop();
> > > > sequence we have there?
> > >
> > > Uhum, well then we oops properly with a null-deref.
> >
> > Cute... Could you dump namei.o (ideally - with namei.s) from your build
> > someplace public?
>
> Yeah, I have at least namei.o
>
> https://drive.google.com/file/d/1AvO1St0YltIrA86DXjp1Xg3ojtS9owGh/view?usp=sharing
*grumble*
Is it reproducible without KASAN? Would be much easier to follow the produced
asm...
next prev parent reply other threads:[~2021-04-04 18:56 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 9:09 [syzbot] WARNING in mntput_no_expire (2) syzbot
2021-04-01 12:16 ` syzbot
2021-04-01 18:32 ` Christian Brauner
2021-04-01 15:45 ` Christian Brauner
2021-04-01 16:09 ` Jens Axboe
2021-04-01 17:46 ` Christian Brauner
2021-04-01 17:59 ` Christian Brauner
2021-04-01 19:11 ` Al Viro
2021-04-04 2:34 ` Al Viro
2021-04-04 2:38 ` Al Viro
2021-04-04 11:34 ` Christian Brauner
2021-04-04 15:56 ` Al Viro
2021-04-04 16:40 ` Christian Brauner
2021-04-04 16:44 ` Al Viro
2021-04-04 17:05 ` Christian Brauner
2021-04-04 18:50 ` Al Viro [this message]
2021-04-04 20:17 ` Al Viro
2021-04-05 11:44 ` Christian Brauner
2021-04-05 16:18 ` Al Viro
2021-04-05 17:08 ` Christian Brauner
2021-04-05 18:23 ` Al Viro
2021-04-05 18:28 ` Al Viro
2021-04-05 20:07 ` Christian Brauner
2021-04-06 1:38 ` Al Viro
2021-04-06 2:24 ` Al Viro
2021-04-06 12:35 ` Christian Brauner
2021-04-06 13:13 ` Al Viro
2021-04-06 13:22 ` Christian Brauner
2021-04-06 14:15 ` Al Viro
2021-04-06 14:23 ` Al Viro
2021-04-06 15:37 ` Jens Axboe
2021-04-06 14:46 ` Christian Brauner
2021-04-04 16:52 ` Christian Brauner
2021-04-04 16:55 ` Christian Brauner
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