Date:   Sat, 13 Jan 2018 08:29:41 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+32b24f3e7c9000c48490@...kaller.appspotmail.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com
Subject: Re: BUG: unable to handle kernel paging request in check_memory_region

On Fri, Jan 12, 2018 at 11:58 PM, syzbot
<syzbot+32b24f3e7c9000c48490@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzkaller hit the following crash on
> c92a9a461dff6140c539c61e457aa97df29517d6
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+32b24f3e7c9000c48490@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.


Daniel, is it the same bug that was fixed by "bpf, array: fix overflow
in max_entries and undefined behavior in index_mask"?


> audit: type=1400 audit(1515790631.378:9): avc:  denied  { sys_chroot } for
> pid=3510 comm="syzkaller602893" capability=18
> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns
> permissive=1
> BUG: unable to handle kernel paging request at ffffed004e875e33
> IP: bytes_is_nonzero mm/kasan/kasan.c:166 [inline]
> IP: memory_is_nonzero mm/kasan/kasan.c:184 [inline]
> IP: memory_is_poisoned_n mm/kasan/kasan.c:210 [inline]
> IP: memory_is_poisoned mm/kasan/kasan.c:241 [inline]
> IP: check_memory_region_inline mm/kasan/kasan.c:257 [inline]
> IP: check_memory_region+0x61/0x190 mm/kasan/kasan.c:267
> PGD 21ffee067 P4D 21ffee067 PUD 21ffec067 PMD 0
> Oops: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3510 Comm: syzkaller602893 Not tainted 4.15.0-rc7+ #259
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:bytes_is_nonzero mm/kasan/kasan.c:166 [inline]
> RIP: 0010:memory_is_nonzero mm/kasan/kasan.c:184 [inline]
> RIP: 0010:memory_is_poisoned_n mm/kasan/kasan.c:210 [inline]
> RIP: 0010:memory_is_poisoned mm/kasan/kasan.c:241 [inline]
> RIP: 0010:check_memory_region_inline mm/kasan/kasan.c:257 [inline]
> RIP: 0010:check_memory_region+0x61/0x190 mm/kasan/kasan.c:267
> RSP: 0018:ffff8801bfa77770 EFLAGS: 00010202
> RAX: ffffed004e875e33 RBX: ffff8802743af19b RCX: ffffffff817deb1c
> RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8802743af198
> RBP: ffff8801bfa77780 R08: 1ffff1004e875e33 R09: ffffed004e875e33
> R10: 0000000000000001 R11: ffffed004e875e33 R12: ffffed004e875e34
> R13: ffff8802743af198 R14: ffff8801bfc9f000 R15: ffff8801c135a680
> FS:  0000000001a1d880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffed004e875e33 CR3: 00000001bfe22003 CR4: 00000000001606f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  memcpy+0x23/0x50 mm/kasan/kasan.c:302
>  memcpy include/linux/string.h:344 [inline]
>  map_lookup_elem+0x4dc/0xbd0 kernel/bpf/syscall.c:584
>  SYSC_bpf kernel/bpf/syscall.c:1711 [inline]
>  SyS_bpf+0x922/0x4400 kernel/bpf/syscall.c:1685
>  entry_SYSCALL_64_fastpath+0x23/0x9a
> RIP: 0033:0x440ac9
> RSP: 002b:00000000007dff68 EFLAGS: 00000203 ORIG_RAX: 0000000000000141
> RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440ac9
> RDX: 0000000000000018 RSI: 0000000020eed000 RDI: 0000000000000001
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000203 R12: 00000000004022a0
> R13: 0000000000402330 R14: 0000000000000000 R15: 0000000000000000
> Code: 89 f8 49 c1 e8 03 49 89 db 49 c1 eb 03 4d 01 cb 4d 01 c1 4d 8d 63 01
> 4c 89 c8 4d 89 e2 4d 29 ca 49 83 fa 10 7f 3d 4d 85 d2 74 33 <41> 80 39 00 75
> 21 48 b8 01 00 00 00 00 fc ff df 4d 01 d1 49 01
> RIP: bytes_is_nonzero mm/kasan/kasan.c:166 [inline] RSP: ffff8801bfa77770
> RIP: memory_is_nonzero mm/kasan/kasan.c:184 [inline] RSP: ffff8801bfa77770
> RIP: memory_is_poisoned_n mm/kasan/kasan.c:210 [inline] RSP:
> ffff8801bfa77770
> RIP: memory_is_poisoned mm/kasan/kasan.c:241 [inline] RSP: ffff8801bfa77770
> RIP: check_memory_region_inline mm/kasan/kasan.c:257 [inline] RSP:
> ffff8801bfa77770
> RIP: check_memory_region+0x61/0x190 mm/kasan/kasan.c:267 RSP:
> ffff8801bfa77770
> CR2: ffffed004e875e33
> ---[ end trace 769bd3705f3abe78 ]---
> Kernel panic - not syncing: Fatal exception
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
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