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BUG: KASAN: stack-out-of-bounds in strnlen+0xc1/0xd0 lib/string.c:498
Read of size 1 at addr ffff8800b8c9fcf4 by task syz-executor7/8208

CPU: 1 PID: 8208 Comm: syz-executor7 Not tainted 4.4.132-g4f75c34 #44
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 e04668cea6d7ac71 ffff8800b8c9f760 ffffffff81e0df8d
 ffffea0002e327c0 ffff8800b8c9fcf4 0000000000000000 ffff8800b8c9fcf4
 ffff8800b8c9fcc0 ffff8800b8c9f798 ffffffff8151526c ffff8800b8c9fcf4
Call Trace:
 [<ffffffff81e0df8d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0df8d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8151526c>] print_address_description+0x6c/0x216 mm/kasan/report.c:252
 [<ffffffff8151558b>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff8151558b>] kasan_report.cold.7+0x175/0x2f7 mm/kasan/report.c:408
 [<ffffffff814f9024>] __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:426
 [<ffffffff81e29a91>] strnlen+0xc1/0xd0 lib/string.c:498
 [<ffffffff81e31b7c>] string.isra.4+0x4c/0x250 lib/vsprintf.c:518
 [<ffffffff81e36d32>] vsnprintf+0x402/0x18e0 lib/vsprintf.c:1907
 [<ffffffff81e3823d>] vscnprintf+0x2d/0x60 lib/vsprintf.c:2010
 [<ffffffff8125cebf>] vprintk_emit+0xdf/0x840 kernel/printk/printk.c:1729
 [<ffffffff8125d648>] vprintk+0x28/0x30 kernel/printk/printk.c:1843
 [<ffffffff8125d66d>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1844
 [<ffffffff81414f88>] printk+0xaf/0xd7 kernel/printk/printk.c:1922
 [<ffffffff8389bd84>] do_ip_vs_set_ctl.cold.37+0x32/0x37 net/netfilter/ipvs/ip_vs_ctl.c:2394
 [<ffffffff830c564d>] nf_sockopt net/netfilter/nf_sockopt.c:105 [inline]
 [<ffffffff830c564d>] nf_setsockopt+0x6d/0xc0 net/netfilter/nf_sockopt.c:114
 [<ffffffff83224d3a>] ip_setsockopt+0x9a/0xb0 net/ipv4/ip_sockglue.c:1227
 [<ffffffff83242858>] tcp_setsockopt+0x88/0xe0 net/ipv4/tcp.c:2643
 [<ffffffff82f2343a>] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2659
 [<ffffffff82f20356>] SYSC_setsockopt net/socket.c:1767 [inline]
 [<ffffffff82f20356>] SyS_setsockopt+0x166/0x260 net/socket.c:1746
 [<ffffffff838c0225>] entry_SYSCALL_64_fastpath+0x22/0x9e

The buggy address belongs to the page:
page:ffffea0002e327c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8800b8c9fb80: f2 f2 00 00 00 00 00 f2 f2 f2 f2 f2 f2 f2 00 00
 ffff8800b8c9fc00: 00 00 00 04 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00
>ffff8800b8c9fc80: 00 00 f2 f2 f2 f2 00 00 00 00 00 00 00 00 04 f2
                                                             ^
 ffff8800b8c9fd00: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8800b8c9fd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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