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SubjectKASAN: use-after-free Read in xfrm_sk_policy_lookup (2)

syzbot found the following crash on:

HEAD commit: f9221a7a Add linux-next specific files for 20190415
git tree: linux-next
console output:
kernel config:
dashboard link:
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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:

BUG: KASAN: use-after-free in xfrm_sk_policy_lookup+0x4aa/0x510
Read of size 2 at addr ffff888097eb6b5e by task syz-executor.3/8005

CPU: 0 PID: 8005 Comm: syz-executor.3 Not tainted 5.1.0-rc4-next-20190415
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+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
__kasan_report.cold+0x1b/0x40 mm/kasan/report.c:316
kasan_report+0x12/0x20 mm/kasan/common.c:623
__asan_report_load2_noabort+0x14/0x20 mm/kasan/generic_report.c:130
xfrm_sk_policy_lookup+0x4aa/0x510 net/xfrm/xfrm_policy.c:2162
xfrm_lookup_with_ifid+0x1de/0x1ce0 net/xfrm/xfrm_policy.c:3046
xfrm_lookup net/xfrm/xfrm_policy.c:3183 [inline]
xfrm_lookup_route+0x3b/0x1f0 net/xfrm/xfrm_policy.c:3194
ip6_dst_lookup_flow+0x189/0x220 net/ipv6/ip6_output.c:1100
inet6_csk_route_socket+0x85d/0xf40 net/ipv6/inet6_connection_sock.c:110
inet6_csk_xmit+0x110/0x5d0 net/ipv6/inet6_connection_sock.c:125
l2tp_xmit_core net/l2tp/l2tp_core.c:1033 [inline]
l2tp_xmit_skb+0x1114/0x13e0 net/l2tp/l2tp_core.c:1135
pppol2tp_sendmsg+0x4a2/0x6b0 net/l2tp/l2tp_ppp.c:329
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xdd/0x130 net/socket.c:661
___sys_sendmsg+0x3e2/0x930 net/socket.c:2260
__sys_sendmmsg+0x1bf/0x4d0 net/socket.c:2355
__do_sys_sendmmsg net/socket.c:2384 [inline]
__se_sys_sendmmsg net/socket.c:2381 [inline]
__x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2381
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
RIP: 0033:0x458c29
Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f948c242c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000458c29
RDX: 0800000000000059 RSI: 0000000020005fc0 RDI: 0000000000000005
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f948c2436d4
R13: 00000000004c5e19 R14: 00000000004da5e0 R15: 00000000ffffffff

Allocated by task 8005:
save_stack+0x45/0xd0 mm/kasan/common.c:76
set_track mm/kasan/common.c:88 [inline]
__kasan_kmalloc mm/kasan/common.c:498 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:471
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:512
kmem_cache_alloc_trace+0x151/0x760 mm/slab.c:3621
kmalloc include/linux/slab.h:547 [inline]
kzalloc include/linux/slab.h:742 [inline]
xfrm_policy_alloc+0x88/0x420 net/xfrm/xfrm_policy.c:383
xfrm_compile_policy+0x254/0x430 net/xfrm/xfrm_user.c:3000
xfrm_user_policy+0x28e/0x820 net/xfrm/xfrm_state.c:2079
do_ipv6_setsockopt.isra.0+0x3b0c/0x49e0 net/ipv6/ipv6_sockglue.c:834
ipv6_setsockopt+0xfc/0x170 net/ipv6/ipv6_sockglue.c:946
udpv6_setsockopt+0x68/0xb0 net/ipv6/udp.c:1570
sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:3120
__sys_setsockopt+0x180/0x280 net/socket.c:2046
__do_sys_setsockopt net/socket.c:2057 [inline]
__se_sys_setsockopt net/socket.c:2054 [inline]
__x64_sys_setsockopt+0xbe/0x150 net/socket.c:2054
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290

Freed by task 8023:
save_stack+0x45/0xd0 mm/kasan/common.c:76
set_track mm/kasan/common.c:88 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:460
kasan_slab_free+0xe/0x10 mm/kasan/common.c:468
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3821
xfrm_policy_destroy_rcu+0x48/0x60 net/xfrm/xfrm_policy.c:407
__rcu_reclaim kernel/rcu/rcu.h:222 [inline]
rcu_do_batch kernel/rcu/tree.c:2092 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2310 [inline]
rcu_core+0xbac/0x1510 kernel/rcu/tree.c:2291
__do_softirq+0x266/0x95a kernel/softirq.c:293

The buggy address belongs to the object at ffff888097eb6940
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 542 bytes inside of
1024-byte region [ffff888097eb6940, ffff888097eb6d40)
The buggy address belongs to the page:
page:ffffea00025fad80 count:1 mapcount:0 mapping:ffff88812c3f0ac0 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000244fb08 ffffea0002643a88 ffff88812c3f0ac0
raw: 0000000000000000 ffff888097eb6040 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888097eb6a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888097eb6a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888097eb6b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888097eb6b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888097eb6c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

This bug is generated by a bot. It may contain errors.
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