On Fri, Feb 1, 2019 at 1:26 AM Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Wed, Jan 30, 2019 at 10:30 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote: > > > > On Wed, Jan 30, 2019 at 4:01 PM syzbot > > <syzbot+1bfc00ca3aabe5bcd4cb@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > 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
