linux-kernel - Re: general protection fault in skb_release

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Date:   Fri, 19 May 2017 14:57:25 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     idaifish@...il.com, "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Cong Wang <xiyou.wangcong@...il.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>
Subject: Re: general protection fault in skb_release_data

On Fri, May 19, 2017 at 12:18 PM,  <idaifish@...il.com> wrote:
> 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!

>
> =======================================================
> 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..
>
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View attachment "ip6_append_data-crash-poc.c" of type "text/x-csrc" (44543 bytes)

Download attachment ".config" of type "application/octet-stream" (129113 bytes)