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From: Christian Brauner <[email protected]>
To: Al Viro <[email protected]>
Cc: Jens Axboe <[email protected]>,
	syzbot <[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [syzbot] WARNING in mntput_no_expire (2)
Date: Sun, 4 Apr 2021 19:05:13 +0200	[thread overview]
Message-ID: <20210404170513.mfl5liccdaxjnpls@wittgenstein> (raw)
In-Reply-To: <[email protected]>

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

Christian

  reply	other threads:[~2021-04-04 17:05 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <[email protected]>
2021-04-01 15:45 ` [syzbot] WARNING in mntput_no_expire (2) 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 [this message]
2021-04-04 18:50                       ` Al Viro
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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