KASAN: use-after-free Read in free_pipe_info

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
c0b6edef0bf0e33c12eaf80c676ff09def011518 (Thu Mar 29 19:58:10 2018 +0000)
tc-testing: Add newline when writing test case files
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=9b83e6b357f8790c65eb

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=5231000850268160
Kernel config:
https://syzkaller.appspot.com/x/.config?id=3327544840960562528
compiler: gcc (GCC) 7.1.1 20170620
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

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Reported-by: syzbot+9b83e6...@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in free_pipe_info+0x266/0x2a0 fs/pipe.c:678
Read of size 8 at addr ffff8801b489a910 by task udevd/5701

CPU: 0 PID: 5701 Comm: udevd Not tainted 4.16.0-rc6+ #288
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+0x194/0x24d lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report+0x23c/0x360 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
free_pipe_info+0x266/0x2a0 fs/pipe.c:678
put_pipe_info+0xb0/0xd0 fs/pipe.c:556
pipe_release+0x1af/0x250 fs/pipe.c:577
__fput+0x327/0x7e0 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x199/0x270 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
do_syscall_64+0x6ec/0x940 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7ff77994e2b0
RSP: 002b:00007ffce684f228 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 20c49ba5e353f7cf RCX: 00007ff77994e2b0
RDX: 0000000000000000 RSI: 00007ffce684f29c RDI: 0000000000000005
RBP: 00000000ffffffff R08: 0000000000000006 R09: 00000020166df354
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000017e9d30
R13: 000000000000317f R14: 00007ffce684f294 R15: 00000000017cb250

Allocated by task 4352:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
__do_kmalloc_node mm/slab.c:3669 [inline]
__kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3683
__kmalloc_reserve.isra.39+0x41/0xd0 net/core/skbuff.c:137
__alloc_skb+0x13b/0x780 net/core/skbuff.c:205
alloc_skb include/linux/skbuff.h:986 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1179 [inline]
netlink_sendmsg+0xa86/0xe60 net/netlink/af_netlink.c:1871
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:639
___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
__sys_sendmsg+0xe5/0x210 net/socket.c:2081
SYSC_sendmsg net/socket.c:2092 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2088
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 4352:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
__cache_free mm/slab.c:3485 [inline]
kfree+0xd9/0x260 mm/slab.c:3800
skb_free_head+0x74/0xb0 net/core/skbuff.c:550
skb_release_data+0x58c/0x790 net/core/skbuff.c:570
skb_release_all+0x4a/0x60 net/core/skbuff.c:627
__kfree_skb net/core/skbuff.c:641 [inline]
consume_skb+0x153/0x490 net/core/skbuff.c:701
netlink_unicast_kernel net/netlink/af_netlink.c:1308 [inline]
netlink_unicast+0x4cc/0x6b0 net/netlink/af_netlink.c:1333
netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:629 [inline]
sock_sendmsg+0xca/0x110 net/socket.c:639
___sys_sendmsg+0x767/0x8b0 net/socket.c:2047
__sys_sendmsg+0xe5/0x210 net/socket.c:2081
SYSC_sendmsg net/socket.c:2092 [inline]
SyS_sendmsg+0x2d/0x50 net/socket.c:2088
do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8801b489a900
which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 16 bytes inside of
1024-byte region [ffff8801b489a900, ffff8801b489ad00)
The buggy address belongs to the page:
page:ffffea0006d22680 count:1 mapcount:0 mapping:ffff8801b489a000 index:0x0
compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801b489a000 0000000000000000 0000000100000007
raw: ffffea000730e6a0 ffffea0007257e20 ffff8801dac00ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801b489a800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b489a880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801b489a900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801b489a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801b489aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.