Re: kernel BUG at net/core/skbuff.c:LINE! (3)

On Sat, Feb 10, 2018 at 12:17 PM, Xin Long [off-list ref] wrote:

On Fri, Feb 2, 2018 at 3:21 AM, syzbot
[off-list ref] wrote:

quoted

Hello,

syzbot hit the following crash on net-next commit
b2fe5fa68642860e7de76167c3111623aa0d5de1 (Wed Jan 31 22:31:10 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+b2bf2652983d23734c5c@syzkaller.appspotmail.com
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skbuff: skb_over_panic: text:000000004b89f3be len:66136 put:66124
head:00000000f255561a data:00000000ccb55e52 tail:0x10310 end:0x6c0
dev:<NULL>

From the raw log, it should be a data chunk.
But I couldn't see how len:66136 happened?
considering that frag_point is always smaller than SCTP_MAX_CHUNK_LEN.

William, Meenakshi,

This crash was bisected to:

commit 84e54fe0a5eaed696dee4019c396f8396f5a908b
Author: William Tu [off-list ref]
Date:   Tue Aug 22 09:40:28 2017 -0700

    gre: introduce native tunnel support for ERSPAN

bisection log:
https://gist.githubusercontent.com/dvyukov/a9661d43b2b519b91540f7466dbc32c1/raw/8df343224177933c8c398be126bb82be99aa0b4b/gistfile1.txt

quoted

------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:104!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 19738 Comm: syz-executor3 Not tainted 4.15.0+ #219
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:skb_panic+0x162/0x1f0 net/core/skbuff.c:100
RSP: 0018:ffff8801c1a6e4e8 EFLAGS: 00010286
RAX: 000000000000008f RBX: ffff8801d0090000 RCX: 0000000000000000
RDX: 000000000000008f RSI: ffffc90003d53000 RDI: ffffed003834dc91
RBP: ffff8801c1a6e550 R08: 1ffff1003834dc1f R09: 0000000000000000
R10: 0000000000000004 R11: 0000000000000000 R12: ffffffff863fe4e0
R13: ffffffff85276640 R14: 000000000001024c R15: ffffffff863fdd20
FS:  00007f69cd01b700(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000718008 CR3: 00000001c71c7006 CR4: 00000000001606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 skb_over_panic net/core/skbuff.c:109 [inline]
 skb_put+0x18d/0x1d0 net/core/skbuff.c:1695
 skb_put_data include/linux/skbuff.h:2049 [inline]
 sctp_packet_pack net/sctp/output.c:473 [inline]
 sctp_packet_transmit+0x1180/0x3750 net/sctp/output.c:606
 sctp_outq_flush+0x121b/0x4060 net/sctp/outqueue.c:1197
 sctp_outq_uncork+0x5a/0x70 net/sctp/outqueue.c:776
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1807 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1210 [inline]
 sctp_do_sm+0x4e0/0x6ed0 net/sctp/sm_sideeffect.c:1181
 sctp_primitive_SEND+0xa0/0xd0 net/sctp/primitive.c:178
 sctp_sendmsg+0x1894/0x35e0 net/sctp/socket.c:2029
 inet_sendmsg+0x11f/0x5e0 net/ipv4/af_inet.c:764
 sock_sendmsg_nosec net/socket.c:630 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:640
 sock_write_iter+0x31a/0x5d0 net/socket.c:909
 call_write_iter include/linux/fs.h:1781 [inline]
 do_iter_readv_writev+0x55c/0x830 fs/read_write.c:653
 do_iter_write+0x154/0x540 fs/read_write.c:932
 vfs_writev+0x18a/0x340 fs/read_write.c:977
 do_writev+0xfc/0x2a0 fs/read_write.c:1012
 SYSC_writev fs/read_write.c:1085 [inline]
 SyS_writev+0x27/0x30 fs/read_write.c:1082
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007f69cd01ac58 EFLAGS: 00000212 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299
RDX: 0000000000000001 RSI: 0000000020f7ffe0 RDI: 0000000000000013
RBP: 00000000000005c5 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f7b18
R13: 00000000ffffffff R14: 00007f69cd01b6d4 R15: 0000000000000000
Code: 04 01 84 c0 74 04 3c 03 7e 23 8b 8b 80 00 00 00 41 57 48 c7 c7 60 dd
3f 86 52 56 4c 89 ea 41 50 4c 89 e6 45 89 f0 e8 c6 d7 25 fd <0f> 0b 4c 89 4d
b8 4c 89 45 c0 48 89 75 c8 48 89 55 d0 e8 47 53
RIP: skb_panic+0x162/0x1f0 net/core/skbuff.c:100 RSP: ffff8801c1a6e4e8
---[ end trace c7cd29819a9b12ab ]---


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