Subject: Re: WARNING in xt_compat_add_offset

From: syzbot <[email-masked]>
Date: Sat, 20 Jul 2019 16:55:05 -0700

syzbot has found a reproducer for the following crash on:

HEAD commit:    abdfd52a Merge tag 'armsoc-defconfig' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=146c4968600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b8e53b1e149c0183
dashboard link: https://syzkaller.appspot.com/bug?extid=276ddebab3382bbf72db
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=159be500600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=139364f0600000

The bug was bisected to:

commit 2035f3ff8eaa29cfb5c8e2160b0f6e85eeb21a95
Author: Florian Westphal <[email-masked]>
Date:   Mon Jan 21 20:54:36 2019 +0000

     netfilter: ebtables: compat: un-break 32bit setsockopt when no rules  
are present

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1462834d200000
final crash:    https://syzkaller.appspot.com/x/report.txt?x=1662834d200000
console output: https://syzkaller.appspot.com/x/log.txt?x=1262834d200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]
Fixes: 2035f3ff8eaa ("netfilter: ebtables: compat: un-break 32bit  
setsockopt when no rules are present")

------------[ cut here ]------------
WARNING: CPU: 1 PID: 9012 at net/netfilter/x_tables.c:649  
xt_compat_add_offset.cold+0x11/0x36 /net/netfilter/x_tables.c:649
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 9012 Comm: syz-executor131 Not tainted 5.2.0+ #64
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack /lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 /lib/dump_stack.c:113
  panic+0x2dc/0x755 /kernel/panic.c:219
  __warn.cold+0x20/0x4c /kernel/panic.c:576
  report_bug+0x263/0x2b0 /lib/bug.c:186
  fixup_bug /arch/x86/kernel/traps.c:179 [inline]
  fixup_bug /arch/x86/kernel/traps.c:174 [inline]
  do_error_trap+0x11b/0x200 /arch/x86/kernel/traps.c:272
  do_invalid_op+0x37/0x50 /arch/x86/kernel/traps.c:291
  invalid_op+0x14/0x20 /arch/x86/entry/entry_64.S:1008
RIP: 0010:xt_compat_add_offset.cold+0x11/0x36 /net/netfilter/x_tables.c:649
Code: 89 ee 48 c7 c7 c0 29 2d 88 e8 0c 76 7b fb 41 bc ea ff ff ff e9 87 88  
ff ff e8 08 d3 91 fb 48 c7 c7 00 2a 2d 88 e8 f0 75 7b fb <0f> 0b 41 bc f4  
ff ff ff e9 01 8b ff ff e8 ea d2 91 fb 48 c7 c7 00
RSP: 0018:ffff8880a382f8d8 EFLAGS: 00010286
RAX: 0000000000000024 RBX: ffff888216b74ad0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff815c3a26 RDI: ffffed1014705f0d
RBP: ffff8880a382f908 R08: 0000000000000024 R09: ffffed1015d260b1
R10: ffffed1015d260b0 R11: ffff8880ae930587 R12: 0000000000000014
R13: 0000000000000060 R14: ffff88808b7b6180 R15: 0000000000000000
  size_entry_mwt /net/bridge/netfilter/ebtables.c:2122 [inline]
  compat_copy_entries+0x10e9/0x1340 /net/bridge/netfilter/ebtables.c:2147
  compat_do_replace+0x3b3/0x680 /net/bridge/netfilter/ebtables.c:2243
  compat_do_ebt_set_ctl+0x22f/0x27e /net/bridge/netfilter/ebtables.c:2325
  compat_nf_sockopt /net/netfilter/nf_sockopt.c:144 [inline]
  compat_nf_setsockopt+0x98/0x140 /net/netfilter/nf_sockopt.c:156
  compat_ip_setsockopt /net/ipv4/ip_sockglue.c:1286 [inline]
  compat_ip_setsockopt+0x106/0x140 /net/ipv4/ip_sockglue.c:1267
  compat_raw_setsockopt+0xe0/0x100 /net/ipv4/raw.c:865
  compat_sock_common_setsockopt+0xb2/0x140 /net/core/sock.c:3141
  __compat_sys_setsockopt+0x185/0x380 /net/compat.c:384
  __do_compat_sys_setsockopt /net/compat.c:397 [inline]
  __se_compat_sys_setsockopt /net/compat.c:394 [inline]
  __ia32_compat_sys_setsockopt+0xbd/0x150 /net/compat.c:394
  do_syscall_32_irqs_on /arch/x86/entry/common.c:332 [inline]
  do_fast_syscall_32+0x27b/0xdb3 /arch/x86/entry/common.c:403
  entry_SYSENTER_compat+0x70/0x7f /arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f489c9
Code: d3 83 c4 10 5b 5e 5d c3 ba 80 96 98 00 eb a9 8b 04 24 c3 8b 34 24 c3  
8b 3c 24 c3 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90  
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000ffaa6d8c EFLAGS: 00000292 ORIG_RAX: 000000000000016e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000080 RSI: 0000000020000000 RDI: 00000000000001fc
RBP: 0000000000000012 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Kernel Offset: disabled
Rebooting in 86400 seconds..