KMSAN: uninit-value in ipv6_find_tlv

From: syzbot <syzbot+8257f4dcef79de670baf@syzkaller.appspotmail.com>
To: davem@davemloft.net, glider@google.com, kuznet@ms2.inr.ac.ru,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org
Subject: KMSAN: uninit-value in ipv6_find_tlv
Date: Tue, 13 Aug 2019 07:48:05 -0700	[thread overview]
Message-ID: <00000000000068a9b7059000ba1a@google.com> (raw)

Hello,

syzbot found the following crash on:

HEAD commit:    61ccdad1 Revert "drm/bochs: Use shadow buffer for bochs fr..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1229a18c600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=27abc558ecb16a3b
dashboard link: https://syzkaller.appspot.com/bug?extid=8257f4dcef79de670baf
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12480dce600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1659dc4a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+8257f4dcef79de670baf@syzkaller.appspotmail.com

==================================================================
BUG: KMSAN: uninit-value in ipv6_find_tlv+0x370/0x3c0  
net/ipv6/exthdrs_core.c:147
CPU: 1 PID: 12844 Comm: syz-executor755 Not tainted 5.3.0-rc3+ #17
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+0x191/0x1f0 lib/dump_stack.c:113
  kmsan_report+0x162/0x2d0 mm/kmsan/kmsan_report.c:109
  __msan_warning+0x75/0xe0 mm/kmsan/kmsan_instr.c:294
  ipv6_find_tlv+0x370/0x3c0 net/ipv6/exthdrs_core.c:147
  ip6_find_1stfragopt+0x2b6/0x500 net/ipv6/output_core.c:102
  ip6_fragment+0x275/0x37d0 net/ipv6/ip6_output.c:775
  __ip6_finish_output+0x753/0x8f0 net/ipv6/ip6_output.c:140
  ip6_finish_output+0x2db/0x420 net/ipv6/ip6_output.c:152
  NF_HOOK_COND include/linux/netfilter.h:294 [inline]
  ip6_output+0x5d3/0x720 net/ipv6/ip6_output.c:175
  dst_output include/net/dst.h:436 [inline]
  ip6_local_out+0x164/0x1d0 net/ipv6/output_core.c:179
  ip6_send_skb net/ipv6/ip6_output.c:1791 [inline]
  ip6_push_pending_frames+0x215/0x4f0 net/ipv6/ip6_output.c:1811
  rawv6_push_pending_frames net/ipv6/raw.c:613 [inline]
  rawv6_sendmsg+0x40da/0x5b10 net/ipv6/raw.c:954
  inet_sendmsg+0x2d8/0x2e0 net/ipv4/af_inet.c:807
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  sock_write_iter+0x599/0x650 net/socket.c:989
  call_write_iter include/linux/fs.h:1870 [inline]
  new_sync_write fs/read_write.c:483 [inline]
  __vfs_write+0xa2c/0xcb0 fs/read_write.c:496
  vfs_write+0x481/0x920 fs/read_write.c:558
  ksys_write+0x265/0x430 fs/read_write.c:611
  __do_sys_write fs/read_write.c:623 [inline]
  __se_sys_write+0x92/0xb0 fs/read_write.c:620
  __x64_sys_write+0x4a/0x70 fs/read_write.c:620
  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x452be9
Code: e8 7c e6 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7  
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
ff 0f 83 1b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbf62544ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006efa08 RCX: 0000000000452be9
RDX: 00000000000041a0 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 00000000006efa00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006efa0c
R13: 00007ffec68fe78f R14: 00007fbf625459c0 R15: 20c49ba5e353f7cf

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:187 [inline]
  kmsan_internal_poison_shadow+0x53/0xa0 mm/kmsan/kmsan.c:146
  kmsan_slab_alloc+0xaa/0x120 mm/kmsan/kmsan_hooks.c:175
  slab_alloc_node mm/slub.c:2790 [inline]
  __kmalloc_node_track_caller+0xb55/0x1320 mm/slub.c:4388
  __kmalloc_reserve net/core/skbuff.c:141 [inline]
  __alloc_skb+0x306/0xa10 net/core/skbuff.c:209
  alloc_skb include/linux/skbuff.h:1056 [inline]
  __ip6_append_data+0x46ad/0x6060 net/ipv6/ip6_output.c:1514
  ip6_append_data+0x3c2/0x650 net/ipv6/ip6_output.c:1683
  rawv6_sendmsg+0x232e/0x5b10 net/ipv6/raw.c:947
  inet_sendmsg+0x2d8/0x2e0 net/ipv4/af_inet.c:807
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  sock_write_iter+0x599/0x650 net/socket.c:989
  call_write_iter include/linux/fs.h:1870 [inline]
  new_sync_write fs/read_write.c:483 [inline]
  __vfs_write+0xa2c/0xcb0 fs/read_write.c:496
  vfs_write+0x481/0x920 fs/read_write.c:558
  ksys_write+0x265/0x430 fs/read_write.c:611
  __do_sys_write fs/read_write.c:623 [inline]
  __se_sys_write+0x92/0xb0 fs/read_write.c:620
  __x64_sys_write+0x4a/0x70 fs/read_write.c:620
  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================

---
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@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches