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BUG: KASAN: stack-out-of-bounds in strnlen+0xc1/0xd0 lib/string.c:498
Read of size 1 at addr ffff8800b4287cc4 by task syzkaller536543/3341

CPU: 0 PID: 3341 Comm: syzkaller536543 Not tainted 4.4.107-g610c835 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 63e5996f9cba928f ffff8800b4287718 ffffffff81d0457d
 ffffea0002d0a1c0 ffff8800b4287cc4 0000000000000000 ffff8800b4287cc4
 ffffffff856b29c0 ffff8800b4287750 ffffffff814fbb23 ffff8800b4287cc4
Call Trace:
 [<ffffffff81d0457d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d0457d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff814fbb23>] print_address_description+0x73/0x260 mm/kasan/report.c:252
 [<ffffffff814fc035>] kasan_report_error mm/kasan/report.c:351 [inline]
 [<ffffffff814fc035>] kasan_report+0x285/0x370 mm/kasan/report.c:408
 [<ffffffff814fc134>] __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:426
 [<ffffffff81d1ff51>] strnlen+0xc1/0xd0 lib/string.c:498
 [<ffffffff81d27bdc>] string.isra.4+0x4c/0x240 lib/vsprintf.c:518
 [<ffffffff81d2d086>] vsnprintf+0x766/0x15f0 lib/vsprintf.c:1907
 [<ffffffff81d2df3d>] vscnprintf+0x2d/0x60 lib/vsprintf.c:2010
 [<ffffffff81266f8b>] vprintk_emit+0xdb/0x850 kernel/printk/printk.c:1729
 [<ffffffff81267728>] vprintk+0x28/0x30 kernel/printk/printk.c:1843
 [<ffffffff8126774d>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1844
 [<ffffffff8141839d>] printk+0xb7/0xe2 kernel/printk/printk.c:1922
 [<ffffffff830982e7>] do_ip_vs_set_ctl+0x9b7/0xba0 net/netfilter/ipvs/ip_vs_ctl.c:2398
 [<ffffffff82f972fa>] compat_nf_sockopt net/netfilter/nf_sockopt.c:145 [inline]
 [<ffffffff82f972fa>] compat_nf_setsockopt+0xfa/0x130 net/netfilter/nf_sockopt.c:155
 [<ffffffff830fe60d>] compat_ip_setsockopt+0x9d/0xf0 net/ipv4/ip_sockglue.c:1255
 [<ffffffff831a4265>] compat_udp_setsockopt+0x45/0x80 net/ipv4/udp.c:2164
 [<ffffffff82df2c42>] compat_sock_common_setsockopt+0xb2/0x140 net/core/sock.c:2670
 [<ffffffff82ed9e79>] C_SYSC_setsockopt net/compat.c:384 [inline]
 [<ffffffff82ed9e79>] compat_SyS_setsockopt+0x149/0x290 net/compat.c:367
 [<ffffffff81006d84>] do_syscall_32_irqs_on arch/x86/entry/common.c:390 [inline]
 [<ffffffff81006d84>] do_fast_syscall_32+0x314/0x890 arch/x86/entry/common.c:457
 [<ffffffff837754d7>] sysenter_flags_fixed+0xd/0x17

The buggy address belongs to the page:
page:ffffea0002d0a1c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8800b4287b80: 00 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 04 f2 f2
 ffff8800b4287c00: f2 f2 f2 f2 00 00 00 00 00 00 00 00 f2 f2 f2 f2
>ffff8800b4287c80: 00 00 00 00 00 00 00 00 04 f2 f2 f2 00 00 00 00
                                           ^
 ffff8800b4287d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8800b4287d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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