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BUG: KASAN: stack-out-of-bounds in vsnprintf+0x18de/0x1b60 lib/vsprintf.c:2267
Read of size 8 at addr ffff8801b18e7aa8 by task syz-executor4/24085

CPU: 1 PID: 24085 Comm: syz-executor4 Not tainted 4.18.0-rc3+ #47
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 vsnprintf+0x18de/0x1b60 lib/vsprintf.c:2267
 vscnprintf+0x2d/0x80 lib/vsprintf.c:2370
 vprintk_emit+0x1ab/0xdf0 kernel/printk/printk.c:1853
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1948
 vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:382
 printk+0xa7/0xcf kernel/printk/printk.c:1981
 show_fault_oops arch/x86/mm/fault.c:671 [inline]
 no_context.cold.36+0x6a/0x98 arch/x86/mm/fault.c:798
 __bad_area_nosemaphore+0x33b/0x3f0 arch/x86/mm/fault.c:902
 bad_area_nosemaphore+0x33/0x40 arch/x86/mm/fault.c:909
 __do_page_fault+0x1db/0xe50 arch/x86/mm/fault.c:1328
 do_page_fault+0xf6/0x8c0 arch/x86/mm/fault.c:1471
 page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1160
RIP: 0010:          (null)
Code: Bad RIP value.
RSP: 0018:ffff8801b18e7f58 EFLAGS: 00010082
RAX: ffff8801cd586700 RBX: 1ffff1003631cfee RCX: 0000000000000000
RDX: 1ffff10039ab0ce0 RSI: 0000000002123940 RDI: ffffffff892a7060
RBP: 0000000000000000 R08: 1ffff100341a5eeb R09: ffff8801a0d2f598
R10: ffffed00359da0d4 R11: ffff8801aced06a3 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea0006c639c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 0000000000000000 ffffffff00000101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801b18e7980: 00 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801b18e7a00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 f2
>ffff8801b18e7a80: 00 00 00 f8 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 00
                                  ^
 ffff8801b18e7b00: 00 00 00 00 00 f1 f1 f1 f1 f8 f2 f2 f2 00 00 00
 ffff8801b18e7b80: 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 f2 f2 f2 f2
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