Re: general protection fault in skb_release_data

On Fri, May 19, 2017 at 5:57 AM, Andrey Konovalov [off-list ref] wrote:

On Fri, May 19, 2017 at 12:18 PM,  [off-list ref] wrote:

quoted

Hi,

I've got the following bug report while fuzzing the
kernel(master-f83246089ca) with syzkaller.

program and config are attached.

Hi!

Thanks for the report!

Adding kernel maintainers.

I can confirm that we've hist this bug multiple times, but never been
able to reproduce it.

I was able to reproduce it on 2ea659a9ef488125eb46da6eb571de5eae5c43f6
(4.12-rc1).

Using the attached syzkaller program I was able to generate C
reproducer, attached. Sometimes I need to run it a few times to
trigger the bug.

@idaifish If you find more bugs please run ./scripts/get_maintainer.pl
to get the list of subsystem maintainers and add them to the
recipients. I've updated instructions of how to report kernel bugs
found with syzkaller in README.

Thanks!

quoted

=======================================================
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: 2 PID: 21599 Comm: syz-executor3 Not tainted 4.11.0-rc8+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
task: ffff88006c16dec0 task.stack: ffff880058bb8000
RIP: 0010:__read_once_size include/linux/compiler.h:254 [inline]
RIP: 0010:compound_head include/linux/page-flags.h:146 [inline]
RIP: 0010:put_page include/linux/mm.h:796 [inline]
RIP: 0010:__skb_frag_unref include/linux/skbuff.h:2613 [inline]
RIP: 0010:skb_release_data+0x201/0x3b0 net/core/skbuff.c:593
RSP: 0018:ffff880058bbf570 EFLAGS: 00010a02
RAX: 11032b488bad1523 RBX: ffff88006c6e8ec8 RCX: ffffc9000190e000
RDX: 1ffff1000d8dd1df RSI: ffffffff8293d7e3 RDI: 88195a445d68a919
RBP: ffff880058bbf5a8 R08: 7bdf27567b31597f R09: 0000000000000000
R10: 00000000000000d2 R11: 7dc9ab6dec891f24 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff88006a475940 R15: 88195a445d68a8f9
FS:  00007fbbc6a34700(0000) GS:ffff88006e400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002004e000 CR3: 000000006b868000 CR4: 00000000000006e0
Call Trace:
 skb_release_all+0x4a/0x60 net/core/skbuff.c:669
 __kfree_skb net/core/skbuff.c:683 [inline]
 kfree_skb+0x85/0x1b0 net/core/skbuff.c:704
 __ip6_append_data.isra.42+0x26ed/0x33b0 net/ipv6/ip6_output.c:1519
 ip6_append_data+0x1a8/0x2f0 net/ipv6/ip6_output.c:1633
 udpv6_sendmsg+0x7bd/0x2360 net/ipv6/udp.c:1264
 inet_sendmsg+0x123/0x3a0 net/ipv4/af_inet.c:762
 sock_sendmsg_nosec net/socket.c:633 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:643
 ___sys_sendmsg+0x79f/0x900 net/socket.c:1997
 __sys_sendmsg+0xd1/0x170 net/socket.c:2031
 SYSC_sendmsg net/socket.c:2042 [inline]
 SyS_sendmsg+0x2d/0x50 net/socket.c:2038
 entry_SYSCALL_64_fastpath+0x1a/0xa9
RIP: 0033:0x44fb79
RSP: 002b:00007fbbc6a33b58 EFLAGS: 00000212 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 000000000044fb79
RDX: 0000000000000000 RSI: 000000002000afc8 RDI: 0000000000000005
RBP: 00000000000003fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000005
R13: 0000000020001000 R14: 0000000000048000 R15: 0000000000000000
Code: 48 83 c0 03 48 c1 e0 04 48 01 d8 48 89 c2 48 c1 ea 03 42 80 3c 2a 00
0f 85 92 01 00 00 4c 8b 38 49 8d 7f 20 48 89 f8 48 c1 e8 03 <42> 80 3c 28 00
0f 85 6f 01 00 00 49 8b 47 20 a8 01 0f 84 3b ff
RIP: __read_once_size include/linux/compiler.h:254 [inline] RSP:
ffff880058bbf570
RIP: compound_head include/linux/page-flags.h:146 [inline] RSP:
ffff880058bbf570
RIP: put_page include/linux/mm.h:796 [inline] RSP: ffff880058bbf570
RIP: __skb_frag_unref include/linux/skbuff.h:2613 [inline] RSP:
ffff880058bbf570
RIP: skb_release_data+0x201/0x3b0 net/core/skbuff.c:593 RSP:
ffff880058bbf570
---[ end trace 46c9f72a66cd8627 ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..

--
You received this message because you are subscribed to the Google Groups
"syzkaller" group.
To unsubscribe from this group and stop receiving emails from it, send an
email to syzkaller+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Hi Andrey, please try following patch
Thanks.