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BUG: KASAN: stack-out-of-bounds in memcmp+0x126/0x160 lib/string.c:768
Read of size 1 at addr ffff8801d81c7ab0 by task syz-executor1/29405

CPU: 1 PID: 29405 Comm: syz-executor1 Not tainted 4.9.135+ #61
 ffff8801d81c7398 ffffffff81b36bf9 ffffea00076071c0 ffff8801d81c7ab0
 0000000000000000 ffff8801d81c7ab0 ffff8801d81c7a98 ffff8801d81c73d0
 ffffffff815009ad ffff8801d81c7ab0 0000000000000001 0000000000000000
Call Trace:
 [<ffffffff81b36bf9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b36bf9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff815009ad>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff81500db7>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81500db7>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff814f2f64>] __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 [<ffffffff81b536f6>] memcmp+0x126/0x160 lib/string.c:768
 [<ffffffff82632c50>] addr_match include/net/xfrm.h:843 [inline]
 [<ffffffff82632c50>] __xfrm6_selector_match net/xfrm/xfrm_policy.c:90 [inline]
 [<ffffffff82632c50>] xfrm_selector_match+0x6a0/0xe40 net/xfrm/xfrm_policy.c:104
 [<ffffffff82633537>] xfrm_sk_policy_lookup+0x147/0x430 net/xfrm/xfrm_policy.c:1283
 [<ffffffff826339dc>] xfrm_lookup+0x1bc/0xc00 net/xfrm/xfrm_policy.c:2242
 [<ffffffff826352b9>] xfrm_lookup_route+0x39/0x140 net/xfrm/xfrm_policy.c:2379
 [<ffffffff826877db>] ip6_dst_lookup_flow+0x17b/0x210 net/ipv6/ip6_output.c:1096
 [<ffffffff8270423c>] rawv6_sendmsg+0x8fc/0x2a70 net/ipv6/raw.c:911
 [<ffffffff82588c63>] inet_sendmsg+0x203/0x4d0 net/ipv4/af_inet.c:770
 [<ffffffff8229437b>] sock_sendmsg_nosec net/socket.c:648 [inline]
 [<ffffffff8229437b>] sock_sendmsg+0xbb/0x110 net/socket.c:658
 [<ffffffff822945f3>] sock_write_iter+0x223/0x3b0 net/socket.c:856
 [<ffffffff81508337>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff81508337>] __vfs_write+0x3d7/0x580 fs/read_write.c:509
 [<ffffffff8150ab87>] vfs_write+0x187/0x520 fs/read_write.c:557
 [<ffffffff8150e9b9>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff8150e9b9>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff810056ef>] do_syscall_64+0x19f/0x550 arch/x86/entry/common.c:285
 [<ffffffff8280ac13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the page:
page:ffffea00076071c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d81c7980: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 00 f2 f2
 ffff8801d81c7a00: f2 f2 f2 f2 00 00 f2 f2 f2 f2 f2 f2 00 00 00 00
>ffff8801d81c7a80: 00 00 00 00 00 00 f2 f2 00 00 00 00 00 00 00 00
                                     ^
 ffff8801d81c7b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801d81c7b80: 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00
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