KASAN: use-after-free Read in xfrm_policy_insert_list

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a26d94bff4d5 net: bridge: remove unneeded variable 'err'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16388ab3400000
kernel config: https://syzkaller.appspot.com/x/.config?x=d9655b05acfc97ff
dashboard link: https://syzkaller.appspot.com/bug?extid=5c4fda922a0a685e2bb5
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [da...@davemloft.net her...@gondor.apana.org.au
linux-...@vger.kernel.org net...@vger.kernel.org
steffen....@secunet.com net...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5c4fda...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in xfrm_policy_insert_list+0xd7f/0x1020
net/xfrm/xfrm_policy.c:1532
Read of size 1 at addr ffff8881c3859899 by task syz-executor4/3341

CPU: 1 PID: 3341 Comm: syz-executor4 Not tainted 4.20.0-rc6+ #352
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+0x244/0x39d lib/dump_stack.c:113
print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
xfrm_policy_insert_list+0xd7f/0x1020 net/xfrm/xfrm_policy.c:1532
xfrm_policy_inexact_insert+0x166/0xee0 net/xfrm/xfrm_policy.c:1195
xfrm_policy_insert+0x639/0x850 net/xfrm/xfrm_policy.c:1570
pfkey_spdadd+0x10f8/0x19d0 net/key/af_key.c:2339
pfkey_process+0x857/0x9a0 net/key/af_key.c:2844
pfkey_sendmsg+0x5e5/0xfb0 net/key/af_key.c:3683
sock_sendmsg_nosec net/socket.c:621 [inline]
sock_sendmsg+0xd5/0x120 net/socket.c:631
___sys_sendmsg+0x7fd/0x930 net/socket.c:2116
__sys_sendmsg+0x11d/0x280 net/socket.c:2154
__do_sys_sendmsg net/socket.c:2163 [inline]
__se_sys_sendmsg net/socket.c:2161 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2161
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457669
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd614ac3c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457669
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd614ac46d4
R13: 00000000004c443a R14: 00000000004d7410 R15: 00000000ffffffff

Allocated by task 2547:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
__do_kmalloc mm/slab.c:3722 [inline]
__kmalloc+0x15b/0x760 mm/slab.c:3731
kmalloc_array include/linux/slab.h:669 [inline]
kcalloc include/linux/slab.h:680 [inline]
alloc_pipe_info+0x2ce/0x5d0 fs/pipe.c:650
get_pipe_inode fs/pipe.c:712 [inline]
create_pipe_files+0x91/0x720 fs/pipe.c:744
__do_pipe_flags+0x45/0x250 fs/pipe.c:781
do_pipe2+0x9d/0x310 fs/pipe.c:829
__do_sys_pipe2 fs/pipe.c:847 [inline]
__se_sys_pipe2 fs/pipe.c:845 [inline]
__x64_sys_pipe2+0x54/0x80 fs/pipe.c:845
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 2547:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3817
free_pipe_info+0x24b/0x300 fs/pipe.c:683
put_pipe_info+0xd0/0xf0 fs/pipe.c:556
pipe_release+0x1de/0x270 fs/pipe.c:577
__fput+0x385/0xa30 fs/file_table.c:278
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881c3859680
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 537 bytes inside of
1024-byte region [ffff8881c3859680, ffff8881c3859a80)
The buggy address belongs to the page:
page:ffffea00070e1600 count:1 mapcount:0 mapping:ffff8881da800ac0
index:0xffff8881c3858000 compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea000654db08 ffffea0007056888 ffff8881da800ac0
raw: ffff8881c3858000 ffff8881c3858000 0000000100000004 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881c3859780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881c3859800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881c3859880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881c3859900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881c3859980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Dmitry Vyukov]

#syz fix: xfrm: policy: fix infinite loop when merging src-nodes

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