syzbot

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BUG: KASAN: out-of-bounds in get_frame_pointer arch/x86/include/asm/stacktrace.h:64 [inline]
BUG: KASAN: out-of-bounds in __unwind_start+0x34b/0x370 arch/x86/kernel/unwind_frame.c:76
Read of size 8 at addr ffff8801c847f8b8 by task syz-executor506/4880

CPU: 1 PID: 4880 Comm: syz-executor506 Not tainted 4.9.155+ #27
 ffff8801c8b776b8 ffffffff81b47871 0000000000000000 ffffea0007211fc0
 ffff8801c847f8b8 0000000000000008 ffffffff810abb0b ffff8801c8b776f0
 ffffffff81502825 0000000000000000 ffff8801c847f8c0 ffff8801c847f8b8
Call Trace:
 [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff81502825>] print_address_description+0x6f/0x238 mm/kasan/report.c:256
 [<ffffffff81502a7a>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<ffffffff81502a7a>] kasan_report mm/kasan/report.c:412 [inline]
 [<ffffffff81502a7a>] kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:397
 [<ffffffff814f4c74>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 [<ffffffff810abb0b>] get_frame_pointer arch/x86/include/asm/stacktrace.h:64 [inline]
 [<ffffffff810abb0b>] __unwind_start+0x34b/0x370 arch/x86/kernel/unwind_frame.c:76
 [<ffffffff810772f9>] unwind_start arch/x86/include/asm/unwind.h:39 [inline]
 [<ffffffff810772f9>] __save_stack_trace+0x59/0xf0 arch/x86/kernel/stacktrace.c:41
 [<ffffffff810773f2>] save_stack_trace_tsk arch/x86/kernel/stacktrace.c:71 [inline]
 [<ffffffff810773f2>] save_stack_trace_tsk+0x42/0x60 arch/x86/kernel/stacktrace.c:66
 [<ffffffff8166adc2>] proc_pid_stack+0x1a2/0x290 fs/proc/base.c:483
 [<ffffffff81663376>] proc_single_show+0xf6/0x160 fs/proc/base.c:785
 [<ffffffff8158241b>] traverse+0x35b/0x910 fs/seq_file.c:124
 [<ffffffff81583757>] seq_read+0x9c7/0x1250 fs/seq_file.c:195
 [<ffffffff8150befc>] do_loop_readv_writev.part.0+0xcc/0x2c0 fs/read_write.c:720
 [<ffffffff8150d606>] do_loop_readv_writev fs/read_write.c:709 [inline]
 [<ffffffff8150d606>] do_readv_writev+0x556/0x7a0 fs/read_write.c:875
 [<ffffffff8150d8d6>] vfs_readv+0x86/0xc0 fs/read_write.c:899
 [<ffffffff8150dd0b>] do_preadv+0x19b/0x240 fs/read_write.c:976
 [<ffffffff815111f1>] SYSC_preadv fs/read_write.c:1026 [inline]
 [<ffffffff815111f1>] SyS_preadv+0x31/0x40 fs/read_write.c:1021
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

The buggy address belongs to the page:
page:ffffea0007211fc0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000000()
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801c847f780: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c847f800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8801c847f880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                           ^
 ffff8801c847f900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801c847f980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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