KMSAN: uninit-value in _decode_session6

KMSAN: uninit-value in _decode_session6

[syzbot]

Hello,

syzbot hit the following crash on  
https://github.com/google/kmsan.git/master commit
e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +0000)
kmsan: temporarily disable visitAsmInstruction() to help syzbot
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=2974b85346f85b586f4d

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=4871594698604544
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=6627248707860932248
compiler: clang version 7.0.0 (trunk 329060) (llvm/trunk 329054)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2974b85346f85b586f4d@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

==================================================================
BUG: KMSAN: uninit-value in _decode_session6+0x6d1/0x1290  
net/ipv6/xfrm6_policy.c:151
CPU: 1 PID: 5714 Comm: blkid Not tainted 4.16.0+ #81
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  <IRQ>
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
  _decode_session6+0x6d1/0x1290 net/ipv6/xfrm6_policy.c:151
  __xfrm_decode_session+0x140/0x1c0 net/xfrm/xfrm_policy.c:2368
  xfrm_decode_session_reverse include/net/xfrm.h:1213 [inline]
  icmpv6_route_lookup net/ipv6/icmp.c:372 [inline]
  icmp6_send+0x305f/0x3460 net/ipv6/icmp.c:551
  icmpv6_send+0xe0/0x110 net/ipv6/ip6_icmp.c:43
  ip6_link_failure+0x8f/0x580 net/ipv6/route.c:2034
  dst_link_failure include/net/dst.h:426 [inline]
  ndisc_error_report+0x101/0x1a0 net/ipv6/ndisc.c:695
  neigh_invalidate+0x385/0x930 net/core/neighbour.c:883
  neigh_timer_handler+0xd85/0x12d0 net/core/neighbour.c:969
  call_timer_fn+0x26a/0x5a0 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0xda7/0x11c0 kernel/time/timer.c:1666
  run_timer_softirq+0x43/0x70 kernel/time/timer.c:1692
  __do_softirq+0x56d/0x93d kernel/softirq.c:285
  invoke_softirq kernel/softirq.c:365 [inline]
  irq_exit+0x202/0x240 kernel/softirq.c:405
  exiting_irq+0xe/0x10 arch/x86/include/asm/apic.h:541
  smp_apic_timer_interrupt+0x64/0x90 arch/x86/kernel/apic/apic.c:1055
  apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:857
  </IRQ>
RIP: 0010:kmsan_get_origin_address_noruntime+0x8f/0x260  
include/linux/mmzone.h:1206
RSP: 0000:ffff880165b0fb40 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff12
RAX: ffff8801e5b0fcc8 RBX: 0000000000000000 RCX: ffff88021fff1580
RDX: 0000000000000580 RSI: 0000000000000000 RDI: ffff880165b0fcc8
RBP: ffff880165b0fb78 R08: 0000000001080020 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000068
R13: 00000000d3a0004b R14: ffff880165b0fcc8 R15: 0000000000000000
  kmsan_set_origin_inline+0x6b/0x120 mm/kmsan/kmsan_instr.c:585
  __msan_poison_alloca+0x15c/0x1d0 mm/kmsan/kmsan_instr.c:647
  handle_mm_fault+0x1c8/0x7ba0 mm/memory.c:4114
  __do_page_fault+0xec4/0x1a10 arch/x86/mm/fault.c:1423
  do_page_fault+0xd3/0x260 arch/x86/mm/fault.c:1500
  page_fault+0x45/0x50 arch/x86/entry/entry_64.S:1151
RIP: 0033:0x7f93ad8e4789
RSP: 002b:00007ffd11b3cf20 EFLAGS: 00010216
RAX: 00007f93ad4742a0 RBX: 00007f93adaf79a8 RCX: 00000000000004a8
RDX: 00007f93ad6a9028 RSI: aaaaaaaaaaaaaaab RDI: 0000000000000000
RBP: 00007ffd11b3d000 R08: 0000000000000001 R09: 0000000000000010
R10: 00007f93ad343a30 R11: 0000000000000206 R12: 00007f93ad325000
R13: 00007f93ad343220 R14: 00007f93ad33d748 R15: 00007f93adaef740

Uninit was stored to memory at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
  kmsan_save_stack mm/kmsan/kmsan.c:293 [inline]
  kmsan_internal_chain_origin+0x12b/0x210 mm/kmsan/kmsan.c:684
  kmsan_memcpy_origins+0x11d/0x170 mm/kmsan/kmsan.c:526
  __msan_memcpy+0x19f/0x1f0 mm/kmsan/kmsan_instr.c:470
  skb_copy_bits+0x63a/0xdb0 net/core/skbuff.c:2046
  __pskb_pull_tail+0x483/0x22e0 net/core/skbuff.c:1883
  pskb_may_pull include/linux/skbuff.h:2112 [inline]
  _decode_session6+0x79f/0x1290 net/ipv6/xfrm6_policy.c:152
  __xfrm_decode_session+0x140/0x1c0 net/xfrm/xfrm_policy.c:2368
  xfrm_decode_session_reverse include/net/xfrm.h:1213 [inline]
  icmpv6_route_lookup net/ipv6/icmp.c:372 [inline]
  icmp6_send+0x305f/0x3460 net/ipv6/icmp.c:551
  icmpv6_send+0xe0/0x110 net/ipv6/ip6_icmp.c:43
  ip6_link_failure+0x8f/0x580 net/ipv6/route.c:2034
  dst_link_failure include/net/dst.h:426 [inline]
  ndisc_error_report+0x101/0x1a0 net/ipv6/ndisc.c:695
  neigh_invalidate+0x385/0x930 net/core/neighbour.c:883
  neigh_timer_handler+0xd85/0x12d0 net/core/neighbour.c:969
  call_timer_fn+0x26a/0x5a0 kernel/time/timer.c:1326
  expire_timers kernel/time/timer.c:1363 [inline]
  __run_timers+0xda7/0x11c0 kernel/time/timer.c:1666
  run_timer_softirq+0x43/0x70 kernel/time/timer.c:1692
  __do_softirq+0x56d/0x93d kernel/softirq.c:285
Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
  kmsan_alloc_meta_for_pages+0x161/0x3a0 mm/kmsan/kmsan.c:814
  kmsan_alloc_page+0x82/0xe0 mm/kmsan/kmsan.c:868
  __alloc_pages_nodemask+0xf5b/0x5dc0 mm/page_alloc.c:4283
  alloc_pages_current+0x6b5/0x970 mm/mempolicy.c:2055
  alloc_pages include/linux/gfp.h:494 [inline]
  skb_page_frag_refill+0x3ba/0x5e0 net/core/sock.c:2208
  sk_page_frag_refill+0xa4/0x340 net/core/sock.c:2228
  __ip6_append_data+0x1a20/0x4bb0 net/ipv6/ip6_output.c:1503
  ip6_append_data+0x40e/0x6b0 net/ipv6/ip6_output.c:1576
  rawv6_sendmsg+0x2787/0x4cc0 net/ipv6/raw.c:928
  inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:764
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg net/socket.c:640 [inline]
  sock_write_iter+0x3b9/0x470 net/socket.c:909
  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
  do_iter_write+0x30d/0xd40 fs/read_write.c:932
  vfs_writev fs/read_write.c:977 [inline]
  do_writev+0x3c9/0x830 fs/read_write.c:1012
  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
  SyS_writev+0x56/0x80 fs/read_write.c:1082
  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
==================================================================


---
This bug is generated by a dumb bot. It may contain errors.
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Re: KMSAN: uninit-value in _decode_session6

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    d2d741e5d189 kmsan: add initialization for shmem pages
git tree:       https://github.com/google/kmsan.git/master
console output: https://syzkaller.appspot.com/x/log.txt?id=6550343064223744
kernel config:   
https://syzkaller.appspot.com/x/.config?id=328654897048964367
dashboard link: https://syzkaller.appspot.com/bug?extid=2974b85346f85b586f4d
compiler:       clang version 7.0.0 (trunk 329391)
syzkaller  
repro:https://syzkaller.appspot.com/x/repro.syz?id=5023772637659136
C reproducer:   https://syzkaller.appspot.com/x/repro.c?id=5102535626981376

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+2974b85346f85b586f4d@syzkaller.appspotmail.com

IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0
==================================================================
BUG: KMSAN: uninit-value in _decode_session6+0x6d2/0x16e0  
net/ipv6/xfrm6_policy.c:151
CPU: 0 PID: 4529 Comm: syz-executor165 Not tainted 4.16.0+ #87
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:683
  _decode_session6+0x6d2/0x16e0 net/ipv6/xfrm6_policy.c:151
  __xfrm_decode_session+0x151/0x200 net/xfrm/xfrm_policy.c:2368
  xfrm_decode_session_reverse include/net/xfrm.h:1213 [inline]
  icmpv6_route_lookup net/ipv6/icmp.c:372 [inline]
  icmp6_send+0x2bf7/0x3730 net/ipv6/icmp.c:551
  icmpv6_send+0xe0/0x110 net/ipv6/ip6_icmp.c:43
  ip6_link_failure+0x8f/0x580 net/ipv6/route.c:2034
  dst_link_failure include/net/dst.h:426 [inline]
  ip6_tnl_xmit+0x1423/0x3af0 net/ipv6/ip6_tunnel.c:1215
  ip6ip6_tnl_xmit net/ipv6/ip6_tunnel.c:1367 [inline]
  ip6_tnl_start_xmit+0x1cc0/0x1ef0 net/ipv6/ip6_tunnel.c:1390
  __netdev_start_xmit include/linux/netdevice.h:4066 [inline]
  netdev_start_xmit include/linux/netdevice.h:4075 [inline]
  xmit_one net/core/dev.c:3026 [inline]
  dev_hard_start_xmit+0x5f1/0xc70 net/core/dev.c:3042
  __dev_queue_xmit+0x27ee/0x3520 net/core/dev.c:3557
  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
  neigh_direct_output+0x42/0x50 net/core/neighbour.c:1390
  neigh_output include/net/neighbour.h:482 [inline]
  ip6_finish_output2+0x1d01/0x2130 net/ipv6/ip6_output.c:120
  ip6_finish_output+0xae9/0xba0 net/ipv6/ip6_output.c:154
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip6_output+0x597/0x6c0 net/ipv6/ip6_output.c:171
  dst_output include/net/dst.h:443 [inline]
  ip6_local_out+0x15e/0x1d0 net/ipv6/output_core.c:176
  ip6_send_skb net/ipv6/ip6_output.c:1682 [inline]
  ip6_push_pending_frames+0x218/0x4d0 net/ipv6/ip6_output.c:1702
  rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
  rawv6_sendmsg+0x4235/0x4fb0 net/ipv6/raw.c:935
  inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:764
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg net/socket.c:640 [inline]
  sock_write_iter+0x3b9/0x470 net/socket.c:909
  call_write_iter include/linux/fs.h:1782 [inline]
  new_sync_write fs/read_write.c:469 [inline]
  __vfs_write+0x7fb/0x9f0 fs/read_write.c:482
  vfs_write+0x463/0x8d0 fs/read_write.c:544
  SYSC_write+0x172/0x360 fs/read_write.c:589
  SyS_write+0x55/0x80 fs/read_write.c:581
  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
RIP: 0033:0x4418b9
RSP: 002b:00007ffece331e68 EFLAGS: 00000217 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004418b9
RDX: 000000000000036b RSI: 0000000020000240 RDI: 0000000000000004
RBP: 00000000006cd018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004025b0
R13: 0000000000402640 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
  slab_post_alloc_hook mm/slab.h:445 [inline]
  slab_alloc_node mm/slub.c:2737 [inline]
  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
  __kmalloc_reserve net/core/skbuff.c:138 [inline]
  pskb_expand_head+0x21d/0x1a70 net/core/skbuff.c:1458
  __pskb_pull_tail+0x1d7/0x2300 net/core/skbuff.c:1878
  pskb_may_pull include/linux/skbuff.h:2112 [inline]
  ip6_tnl_parse_tlv_enc_lim+0x7f5/0xa90 net/ipv6/ip6_tunnel.c:411
  ip6ip6_tnl_xmit net/ipv6/ip6_tunnel.c:1326 [inline]
  ip6_tnl_start_xmit+0x911/0x1ef0 net/ipv6/ip6_tunnel.c:1390
  __netdev_start_xmit include/linux/netdevice.h:4066 [inline]
  netdev_start_xmit include/linux/netdevice.h:4075 [inline]
  xmit_one net/core/dev.c:3026 [inline]
  dev_hard_start_xmit+0x5f1/0xc70 net/core/dev.c:3042
  __dev_queue_xmit+0x27ee/0x3520 net/core/dev.c:3557
  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
  neigh_direct_output+0x42/0x50 net/core/neighbour.c:1390
  neigh_output include/net/neighbour.h:482 [inline]
  ip6_finish_output2+0x1d01/0x2130 net/ipv6/ip6_output.c:120
  ip6_finish_output+0xae9/0xba0 net/ipv6/ip6_output.c:154
  NF_HOOK_COND include/linux/netfilter.h:277 [inline]
  ip6_output+0x597/0x6c0 net/ipv6/ip6_output.c:171
  dst_output include/net/dst.h:443 [inline]
  ip6_local_out+0x15e/0x1d0 net/ipv6/output_core.c:176
  ip6_send_skb net/ipv6/ip6_output.c:1682 [inline]
  ip6_push_pending_frames+0x218/0x4d0 net/ipv6/ip6_output.c:1702
  rawv6_push_pending_frames net/ipv6/raw.c:616 [inline]
  rawv6_sendmsg+0x4235/0x4fb0 net/ipv6/raw.c:935
  inet_sendmsg+0x48d/0x740 net/ipv4/af_inet.c:764
  sock_sendmsg_nosec net/socket.c:630 [inline]
  sock_sendmsg net/socket.c:640 [inline]
  sock_write_iter+0x3b9/0x470 net/socket.c:909
  call_write_iter include/linux/fs.h:1782 [inline]
  new_sync_write fs/read_write.c:469 [inline]
  __vfs_write+0x7fb/0x9f0 fs/read_write.c:482
  vfs_write+0x463/0x8d0 fs/read_write.c:544
  SYSC_write+0x172/0x360 fs/read_write.c:589
  SyS_write+0x55/0x80 fs/read_write.c:581
  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
==================================================================