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BUG: KASAN: stack-out-of-bounds in string+0x25b/0x2a0 lib/vsprintf.c:592
Read of size 1 at addr ffff880191f67c24 by task syz-executor6/11771

CPU: 1 PID: 11771 Comm: syz-executor6 Not tainted 4.9.109-ge1815b3 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff880191f67638 ffffffff81eb3e29 ffffea000647d9c0 ffff880191f67c24
 0000000000000000 ffff880191f67c24 0000000000000034 ffff880191f67670
 ffffffff81567a89 ffff880191f67c24 0000000000000001 0000000000000000
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81567a89>] print_address_description+0x6c/0x234 mm/kasan/report.c:256
 [<ffffffff81567e93>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81567e93>] kasan_report.cold.6+0x242/0x2fe mm/kasan/report.c:412
 [<ffffffff8153ba84>] __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 [<ffffffff81ed624b>] string+0x25b/0x2a0 lib/vsprintf.c:592
 [<ffffffff81edf376>] vsnprintf+0x406/0x1840 lib/vsprintf.c:2044
 [<ffffffff81ee07dd>] vscnprintf+0x2d/0x60 lib/vsprintf.c:2147
 [<ffffffff8125f264>] vprintk_emit+0xf4/0x790 kernel/printk/printk.c:1847
 [<ffffffff8125f928>] vprintk+0x28/0x30 kernel/printk/printk.c:1913
 [<ffffffff8125f94d>] vprintk_default+0x1d/0x30 kernel/printk/printk.c:1914
 [<ffffffff8142ca8c>] vprintk_func kernel/printk/internal.h:36 [inline]
 [<ffffffff8142ca8c>] printk+0xaf/0xd7 kernel/printk/printk.c:1975
 [<ffffffff839d2ac9>] do_ip_vs_set_ctl.cold.36+0x34/0x39 net/netfilter/ipvs/ip_vs_ctl.c:2435
 [<ffffffff831df08d>] compat_nf_sockopt net/netfilter/nf_sockopt.c:145 [inline]
 [<ffffffff831df08d>] compat_nf_setsockopt+0x10d/0x130 net/netfilter/nf_sockopt.c:155
 [<ffffffff833491d7>] compat_ip_setsockopt+0xa7/0xe0 net/ipv4/ip_sockglue.c:1273
 [<ffffffff833f79da>] compat_udp_setsockopt+0x4a/0x90 net/ipv4/udp.c:2101
 [<ffffffff835b4b14>] compat_ipv6_setsockopt+0xb4/0x1d0 net/ipv6/ipv6_sockglue.c:925
 [<ffffffff833526c7>] inet_csk_compat_setsockopt+0x97/0x120 net/ipv4/inet_connection_sock.c:914
 [<ffffffff8336901d>] compat_tcp_setsockopt+0x3d/0x70 net/ipv4/tcp.c:2769
 [<ffffffff8301d854>] compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:2717
 [<ffffffff8311c1ec>] C_SYSC_setsockopt net/compat.c:399 [inline]
 [<ffffffff8311c1ec>] compat_SyS_setsockopt+0x14c/0x2a0 net/compat.c:382
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fb090>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137

The buggy address belongs to the page:
page:ffffea000647d9c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x8000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880191f67b00: f2 f2 f2 f2 00 00 00 00 00 04 f2 f2 f2 f2 f2 f2
 ffff880191f67b80: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 00 00 00 00
>ffff880191f67c00: 00 00 00 00 04 f2 f2 f2 00 00 00 00 00 00 00 00
                               ^
 ffff880191f67c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff880191f67d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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