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BUG: KASAN: stack-out-of-bounds in strnlen+0xc1/0xd0 lib/string.c:498
Read of size 1 at addr ffff8801b82efc84 by task syz-executor2/8317

CPU: 0 PID: 8317 Comm: syz-executor2 Not tainted 4.4.133-g54f36ea #50
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 24effd3f42f2b718 ffff8801b82ef6f0 ffffffff81e0e4cd
 ffffea0006e0bbc0 ffff8801b82efc84 0000000000000000 ffff8801b82efc84
 ffff8801b82efc50 ffff8801b82ef728 ffffffff815154dc ffff8801b82efc84
Call Trace:
 [<ffffffff81e0e4cd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0e4cd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff815154dc>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff815157fb>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff815157fb>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f9294>] __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:426
 [<ffffffff81e29fd1>] strnlen+0xc1/0xd0 lib/string.c:498
 [<ffffffff81e320bc>] string.isra.4+0x4c/0x250 lib/vsprintf.c:518
 [<ffffffff81e37272>] vsnprintf+0x402/0x18e0 lib/vsprintf.c:1907
 [<ffffffff81e3877d>] vscnprintf+0x2d/0x60 lib/vsprintf.c:2010
 [<ffffffff8125cf7f>] vprintk_emit+0xdf/0x840 kernel/printk/printk.c:1729
 [<ffffffff8125d708>] vprintk+0x28/0x30 kernel/printk/printk.c:1843
 [<ffffffff8125d72d>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1844
 [<ffffffff814150e8>] printk+0xaf/0xd7 kernel/printk/printk.c:1922
 [<ffffffff8389caa4>] do_ip_vs_set_ctl.cold.37+0x32/0x37 net/netfilter/ipvs/ip_vs_ctl.c:2394
 [<ffffffff830c5c6d>] compat_nf_sockopt net/netfilter/nf_sockopt.c:145 [inline]
 [<ffffffff830c5c6d>] compat_nf_setsockopt+0x10d/0x130 net/netfilter/nf_sockopt.c:155
 [<ffffffff83225407>] compat_ip_setsockopt+0xa7/0xe0 net/ipv4/ip_sockglue.c:1253
 [<ffffffff8322e657>] inet_csk_compat_setsockopt+0x97/0x120 net/ipv4/inet_connection_sock.c:914
 [<ffffffff83242efd>] compat_tcp_setsockopt+0x3d/0x70 net/ipv4/tcp.c:2654
 [<ffffffff82f238d4>] compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:2670
 [<ffffffff8300a5ec>] C_SYSC_setsockopt net/compat.c:385 [inline]
 [<ffffffff8300a5ec>] compat_SyS_setsockopt+0x14c/0x2a0 net/compat.c:368
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:392 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:459
 [<ffffffff838c28aa>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the page:
page:ffffea0006e0bbc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b82efb80: 00 00 00 00 00 04 f2 f2 f2 f2 f2 f2 00 00 00 00
 ffff8801b82efc00: 00 00 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00 00
>ffff8801b82efc80: 04 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
                   ^
 ffff8801b82efd00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801b82efd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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