KMSAN: uninit-value in rtm_new_nexthop

* KMSAN: uninit-value in rtm_new_nexthop
@ 2019-08-21 22:38 syzbot
  2019-08-22  3:31 ` David Ahern
  0 siblings, 1 reply; 2+ messages in thread
From: syzbot @ 2019-08-21 22:38 UTC (permalink / raw)
  To: davem, dsahern, glider, kuznet, linux-kernel, netdev,
	syzkaller-bugs, yoshfuji

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=1596d33c600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=27abc558ecb16a3b
dashboard link: https://syzkaller.appspot.com/bug?extid=4f3abbb335d1bed2287c
compiler:       clang version 9.0.0 (/home/glider/llvm/clang  
80fee25776c2fb61e74c1ecb1a523375c2500b69)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15733302600000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1028e9e2600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4f3abbb335d1bed2287c@syzkaller.appspotmail.com

==================================================================
BUG: KMSAN: uninit-value in rtm_to_nh_config net/ipv4/nexthop.c:1317  
[inline]
BUG: KMSAN: uninit-value in rtm_new_nexthop+0x447/0x98e0  
net/ipv4/nexthop.c:1474
CPU: 0 PID: 11026 Comm: syz-executor768 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
  rtm_to_nh_config net/ipv4/nexthop.c:1317 [inline]
  rtm_new_nexthop+0x447/0x98e0 net/ipv4/nexthop.c:1474
  rtnetlink_rcv_msg+0x115a/0x1580 net/core/rtnetlink.c:5223
  netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
  rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5241
  netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
  netlink_unicast+0xf6c/0x1050 net/netlink/af_netlink.c:1328
  netlink_sendmsg+0x110f/0x1330 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  ___sys_sendmsg+0x14ff/0x1590 net/socket.c:2311
  __sys_sendmsg net/socket.c:2356 [inline]
  __do_sys_sendmsg net/socket.c:2365 [inline]
  __se_sys_sendmsg+0x305/0x460 net/socket.c:2363
  __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2363
  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
RIP: 0033:0x4401e9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffef5128b58 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401e9
RDX: 0000000000000000 RSI: 0000000020000400 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a70
R13: 0000000000401b00 R14: 0000000000000000 R15: 0000000000000000

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]
  netlink_alloc_large_skb net/netlink/af_netlink.c:1174 [inline]
  netlink_sendmsg+0x783/0x1330 net/netlink/af_netlink.c:1892
  sock_sendmsg_nosec net/socket.c:637 [inline]
  sock_sendmsg net/socket.c:657 [inline]
  ___sys_sendmsg+0x14ff/0x1590 net/socket.c:2311
  __sys_sendmsg net/socket.c:2356 [inline]
  __do_sys_sendmsg net/socket.c:2365 [inline]
  __se_sys_sendmsg+0x305/0x460 net/socket.c:2363
  __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2363
  do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:297
  entry_SYSCALL_64_after_hwframe+0x63/0xe7
==================================================================

---
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