Re: general protection fault in fib6_add (2)

[David Ahern <dsahern@gmail.com>]

[ +weiwan@google.com ]

On 1/2/18 3:58 PM, syzbot wrote:
> Hello,
> 
> syzkaller hit the following crash on
> 61233580f1f33c50e159c50e24d80ffd2ba2e06b
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
> 
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+0693adff3f83403dc5da@syzkaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
> 
> audit: type=1400 audit(1514594846.496:7): avc:  denied  { map } for 
> pid=3201 comm="syzkaller001778" path="/root/syzkaller001778299"
> dev="sda1" ino=16481
> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
> IPv6: Can't replace route, no match found
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3201 Comm: syzkaller001778 Not tainted 4.15.0-rc5+ #151
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:fib6_add+0x736/0x15a0 net/ipv6/ip6_fib.c:1244
> RSP: 0018:ffff8801c7626a70 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000020 RCX: ffffffff84794465
> RDX: 0000000000000004 RSI: ffff8801d38935f0 RDI: 0000000000000282
> RBP: ffff8801c7626da0 R08: 1ffff10038ec4c35 R09: 0000000000000000
> R10: ffff8801c7626c68 R11: 0000000000000000 R12: 00000000fffffffe
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000009
> FS:  0000000000000000(0000) GS:ffff8801db200000(0063)
> knlGS:0000000009b70840
> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> CR2: 0000000020be1000 CR3: 00000001d585a006 CR4: 00000000001606f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  __ip6_ins_rt+0x6c/0x90 net/ipv6/route.c:1006
>  ip6_route_multipath_add+0xd14/0x16c0 net/ipv6/route.c:3833
>  inet6_rtm_newroute+0xdc/0x160 net/ipv6/route.c:3957
>  rtnetlink_rcv_msg+0x733/0x1020 net/core/rtnetlink.c:4411
>  netlink_rcv_skb+0x21e/0x460 net/netlink/af_netlink.c:2408
>  rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4423
>  netlink_unicast_kernel net/netlink/af_netlink.c:1275 [inline]
>  netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1301
>  netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1864
>  sock_sendmsg_nosec net/socket.c:636 [inline]
>  sock_sendmsg+0xca/0x110 net/socket.c:646
>  sock_write_iter+0x31a/0x5d0 net/socket.c:915
>  call_write_iter include/linux/fs.h:1772 [inline]
>  do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653
>  do_iter_write+0x154/0x540 fs/read_write.c:932
>  compat_writev+0x225/0x420 fs/read_write.c:1246
>  do_compat_writev+0x115/0x220 fs/read_write.c:1267
>  C_SYSC_writev fs/read_write.c:1278 [inline]
>  compat_SyS_writev+0x26/0x30 fs/read_write.c:1274
>  do_syscall_32_irqs_on arch/x86/entry/common.c:327 [inline]
>  do_fast_syscall_32+0x3ee/0xf9d arch/x86/entry/common.c:389
>  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:125
> RIP: 0023:0xf7f1fc79
> RSP: 002b:00000000ffb61bfc EFLAGS: 00000203 ORIG_RAX: 0000000000000092
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000204aaff0
> RDX: 0000000000000001 RSI: 0000000000000167 RDI: 0000000000000010
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> Code: f1 a9 f6 fc e8 2c f2 e2 fc 85 c0 0f 85 d5 03 00 00 49 8d 5e 20 e8
> db a9 f6 fc 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c
> 02 00 0f 85 5a 0c 00 00 4d 39 ee 4d 8b 7e 20 0f 95 c0 4c
> RIP: fib6_add+0x736/0x15a0 net/ipv6/ip6_fib.c:1244 RSP: ffff8801c7626a70
> ---[ end trace 956c65133fcfff88 ]---
> 
> 
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@googlegroups.com.
> 
> syzbot will keep track of this bug report.
> If you forgot to add the Reported-by tag, once the fix for this bug is
> merged
> into any tree, please reply to this email with:
> #syz fix: exact-commit-title
> If you want to test a patch for this bug, please reply with:
> #syz test: git://repo/address.git branch
> and provide the patch inline or as an attachment.
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line in the email body.