RE: general protection fault in __ip_append_data

[Jon Maloy]

> -----Original Message-----
> From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Sent: 12-Dec-18 06:03
> To: syzbot+aab62b9c7b12e7c6ab0b@xxxxxxxxxxxxxxxxxxxxxxxxx; Jon Maloy
> <jon.maloy@xxxxxxxxxxxx>; Ying Xue <ying.xue@xxxxxxxxxxxxx>; David
> Miller <davem@xxxxxxxxxxxxx>; tipc-discussion@xxxxxxxxxxxxxxxxxxxxx
> Cc: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>; LKML <linux-
> kernel@xxxxxxxxxxxxxxx>; netdev <netdev@xxxxxxxxxxxxxxx>; syzkaller-bugs
> <syzkaller-bugs@xxxxxxxxxxxxxxxx>; Hideaki YOSHIFUJI <yoshfuji@linux-
> ipv6.org>
> Subject: Re: general protection fault in __ip_append_data
> 
> On Wed, Dec 12, 2018 at 11:57 AM syzbot
> <syzbot+aab62b9c7b12e7c6ab0b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hello,
> >
> > syzbot found the following crash on:
> >
> > HEAD commit:    f5d582777bcb Merge branch 'for-linus' of git://git.kernel...
> > git tree:       upstream
> > console output:
> > https://syzkaller.appspot.com/x/log.txt?x=16e03afb400000
> > kernel config:
> > https://syzkaller.appspot.com/x/.config?x=c8970c89a0efbb23
> > dashboard link:
> https://syzkaller.appspot.com/bug?extid=aab62b9c7b12e7c6ab0b
> > compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> > syz repro:
> https://syzkaller.appspot.com/x/repro.syz?x=13bb9c8b400000
> > C reproducer:
> https://syzkaller.appspot.com/x/repro.c?x=1261667d400000
> 
> From the reproducer it looks like a dup of TIPC bug:
> 
> #syz dup: KASAN: use-after-free Read in kfree_skb (2)

Agree with that, although it is not totally obvious. 
Let's see what the further testing gives after Cong's patch is applied.

///jon

> 
> 
> 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+aab62b9c7b12e7c6ab0b@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > Enabling of bearer <udp:syz1> rejected, already enabled Enabling of
> > bearer <udp:syz1> rejected, already enabled Enabling of bearer
> > <udp:syz1> rejected, already enabled
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] PREEMPT SMP KASAN
> > CPU: 1 PID: 16 Comm: ksoftirqd/1 Not tainted 4.20.0-rc6+ #371 Hardware
> > name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google
> > 01/01/2011
> > RIP: 0010:__ip_append_data.isra.48+0x31a/0x29b0
> > net/ipv4/ip_output.c:896
> > Code: c7 85 c8 fd ff ff 00 00 00 00 0f 85 12 10 00 00 e8 7b c1 e0 fa
> > 48 8b
> > 95 48 fe ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00
> > 0f
> > 85 e5 22 00 00 48 8b 85 48 fe ff ff 48 8b 18 48 b8
> > RSP: 0018:ffff8881d9b569c0 EFLAGS: 00010246
> > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff869ec275
> > RDX: 0000000000000000 RSI: ffffffff869ec2f5 RDI: 0000000000000001
> > RBP: ffff8881d9b56c28 R08: ffff8881d9b4a440 R09: ffffffff86b113b0
> > R10: ffff8881d9b56da0 R11: 0000000000000000 R12: ffff8881d2c18a88
> > R13: ffffffff86258ba0 R14: ffffffff8bc37110 R15: ffff8881d2c18cd8
> > FS:  0000000000000000(0000) GS:ffff8881daf00000(0000)
> > knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020001ac0 CR3: 00000001cb6ea000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call
> > Trace:
> >   ip_append_data.part.49+0xef/0x170 net/ipv4/ip_output.c:1197
> >   ip_append_data+0x6d/0x90 net/ipv4/ip_output.c:1186
> >   icmp_push_reply+0x18e/0x540 net/ipv4/icmp.c:375
> >   icmp_send+0x1544/0x1bd0 net/ipv4/icmp.c:736
> >   __udp4_lib_rcv+0x2484/0x32e0 net/ipv4/udp.c:2233
> >   udp_rcv+0x21/0x30 net/ipv4/udp.c:2392
> >   ip_local_deliver_finish+0x2e9/0xda0 net/ipv4/ip_input.c:215
> >   NF_HOOK include/linux/netfilter.h:289 [inline]
> >   ip_local_deliver+0x1e9/0x750 net/ipv4/ip_input.c:256
> >   dst_input include/net/dst.h:450 [inline]
> >   ip_rcv_finish+0x1f9/0x300 net/ipv4/ip_input.c:415
> >   NF_HOOK include/linux/netfilter.h:289 [inline]
> >   ip_rcv+0xed/0x600 net/ipv4/ip_input.c:524
> >   __netif_receive_skb_one_core+0x14d/0x200 net/core/dev.c:4946
> >   __netif_receive_skb+0x2c/0x1e0 net/core/dev.c:5056
> >   process_backlog+0x24e/0x7a0 net/core/dev.c:5864
> >   napi_poll net/core/dev.c:6287 [inline]
> >   net_rx_action+0x7fa/0x19b0 net/core/dev.c:6353
> >   __do_softirq+0x308/0xb7e kernel/softirq.c:292
> >   run_ksoftirqd+0x5e/0x100 kernel/softirq.c:654
> >   smpboot_thread_fn+0x68b/0xa00 kernel/smpboot.c:164
> >   kthread+0x35a/0x440 kernel/kthread.c:246
> >   ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 Modules linked
> > in:
> > ---[ end trace 762165cda5fdc138 ]---
> > Enabling of bearer <udp:syz1> rejected, already enabled
> > RIP: 0010:__ip_append_data.isra.48+0x31a/0x29b0
> > net/ipv4/ip_output.c:896
> > Code: c7 85 c8 fd ff ff 00 00 00 00 0f 85 12 10 00 00 e8 7b c1 e0 fa
> > 48 8b
> > 95 48 fe ff ff 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00
> > 0f
> > 85 e5 22 00 00 48 8b 85 48 fe ff ff 48 8b 18 48 b8 Enabling of bearer
> > <udp:syz1> rejected, already enabled
> > RSP: 0018:ffff8881d9b569c0 EFLAGS: 00010246
> > RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff869ec275
> > RDX: 0000000000000000 RSI: ffffffff869ec2f5 RDI: 0000000000000001
> > RBP: ffff8881d9b56c28 R08: ffff8881d9b4a440 R09: ffffffff86b113b0
> > R10: ffff8881d9b56da0 R11: 0000000000000000 R12: ffff8881d2c18a88
> > R13: ffffffff86258ba0 R14: ffffffff8bc37110 R15: ffff8881d2c18cd8
> > Enabling of bearer <udp:syz1> rejected, already enabled
> > FS:  0000000000000000(0000) GS:ffff8881daf00000(0000)
> > knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020001ac0 CR3: 000000000946a000 CR4: 00000000001406e0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> >
> >
> > ---
> > This bug is generated by a bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for more information about syzbot.
> > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxxx
> >
> > syzbot will keep track of this bug report. See:
> > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> > syzbot.
> > syzbot can test patches for this bug, for details see:
> > https://goo.gl/tpsmEJ#testing-patches
> >
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