From: Paul Moore <paul@paul-moore.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
David Miller <davem@davemloft.net>,
linux-hams <linux-hams@vger.kernel.org>,
netdev <netdev@vger.kernel.org>,
syzbot <syzbot+1bfc00ca3aabe5bcd4cb@syzkaller.appspotmail.com>,
Eric Paris <eparis@parisplace.org>,
LKML <linux-kernel@vger.kernel.org>,
Stephen Smalley <sds@tycho.nsa.gov>,
selinux@vger.kernel.org,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: Re: KASAN: use-after-free Read in selinux_netlbl_socket_setsockopt
Date: Fri, 1 Feb 2019 11:48:21 -0500 [thread overview]
Message-ID: <CAHC9VhRkDLsQUAHUHYYKO=6vAZxDdw2Dwf+O1QKKQjckMNa1Rg@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+Yk=bsS7Ti3PjeZm8yG_txt=orBztowHwddHRP_MzuTxw@mail.gmail.com>
On Fri, Feb 1, 2019 at 1:26 AM Dmitry Vyukov <dvyukov@google.com> wrote:
> On Wed, Jan 30, 2019 at 10:30 PM Paul Moore <paul@paul-moore.com> wrote:
> >
> > On Wed, Jan 30, 2019 at 4:01 PM syzbot
> > <syzbot+1bfc00ca3aabe5bcd4cb@syzkaller.appspotmail.com> wrote:
> > >
> > > Hello,
> > >
> > > syzbot found the following crash on:
> > >
> > > HEAD commit: 62967898789d Merge git://git.kernel.org/pub/scm/linux/kern..
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=167fdef8c00000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=4fceea9e2d99ac20
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=1bfc00ca3aabe5bcd4cb
> > > compiler: gcc (GCC) 9.0.0 20181231 (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+1bfc00ca3aabe5bcd4cb@syzkaller.appspotmail.com
> > >
> > > 8021q: adding VLAN 0 to HW filter on device team0
> > > ==================================================================
> > > BUG: KASAN: use-after-free in selinux_netlbl_socket_setsockopt+0x49b/0x510
> > > security/selinux/netlabel.c:525
> > > Read of size 8 at addr ffff8880a63cf078 by task syz-executor3/18477
> > >
> > > CPU: 1 PID: 18477 Comm: syz-executor3 Not tainted 5.0.0-rc4+ #51
> > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > > Google 01/01/2011
> > > Call Trace:
> > > __dump_stack lib/dump_stack.c:77 [inline]
> > > dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
> > > print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
> > > kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
> > > __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
> > > selinux_netlbl_socket_setsockopt+0x49b/0x510
> > > security/selinux/netlabel.c:525
> >
> > At first glance this seems odd. The line above is simply
> > dereferencing sock->sk_security (getting the "sksec"), which we also
> > do higher up selinux_socket_setsockopt() via sock_has_perm(). Unless
> > somehow the socket is being released/freed in the middle of a
> > setsockopt() syscall this looks like maybe it's something else?
>
> Hi Paul,
>
> Searching for af_netrom across other syzbot bugs:
> https://groups.google.com/forum/#!searchin/syzkaller-bugs/af_netrom%7Csort:date
>
> I see at least:
> https://syzkaller.appspot.com/bug?extid=b0b1952f5864b4009b09
> https://syzkaller.appspot.com/bug?extid=febf3c50d4262e578b1c
> https://syzkaller.appspot.com/bug?extid=defa700d16f1bd1b9a05
>
> Which suggests there are some serious lifetime problems in netrom
> sockets. That would probably explain this crash as well.
That definitely looks plausible. While I'm not one to say it could
*never* be the SELinux/NetLabel code, I can say that the SELinux code
path in question hasn't changed in some time so I would be a little
surprised if it was suddenly broken.
> +netrom maintainers, does this explanation look plausible to you?
> should we dup this crash onto one of the other netrom bugs? and
> perhaps these netrom bugs across themselves too?
--
paul moore
www.paul-moore.com
next prev parent reply other threads:[~2019-02-01 16:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-30 21:01 KASAN: use-after-free Read in selinux_netlbl_socket_setsockopt syzbot
2019-01-30 21:30 ` Paul Moore
2019-02-01 6:26 ` Dmitry Vyukov
2019-02-01 16:48 ` Paul Moore [this message]
2019-02-01 17:58 ` Cong Wang
2019-02-04 8:04 ` Dmitry Vyukov
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