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From:   Daniel Axtens <dja@axtens.net>
To:     Dmitry Vyukov <dvyukov@google.com>,
        syzbot <syzbot+82e323920b78d54aaed5@syzkaller.appspotmail.com>,
        kasan-dev <kasan-dev@googlegroups.com>
Cc:     Andrii Nakryiko <andriin@fb.com>,
        Alexei Starovoitov <ast@kernel.org>, bpf <bpf@vger.kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Song Liu <songliubraving@fb.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Yonghong Song <yhs@fb.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>
Subject: Re: BUG: unable to handle kernel paging request in pcpu_alloc
In-Reply-To: <CACT4Y+ZTXKP0MAT3ivr5HO-skZOjSVdz7RbDoyc522_Nbk8nKQ@mail.gmail.com>
References: <000000000000314c120598dc69bd@google.com> <CACT4Y+ZTXKP0MAT3ivr5HO-skZOjSVdz7RbDoyc522_Nbk8nKQ@mail.gmail.com>
Date:   Thu, 05 Dec 2019 15:35:21 +1100
Message-ID: <877e3be6eu.fsf@dja-thinkpad.axtens.net>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

>> HEAD commit:    1ab75b2e Add linux-next specific files for 20191203
>> git tree:       linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=10edf2eae00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=de1505c727f0ec20
>> dashboard link: https://syzkaller.appspot.com/bug?extid=82e323920b78d54aaed5
>> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=156ef061e00000
>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11641edae00000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+82e323920b78d54aaed5@syzkaller.appspotmail.com
>
> +Daniel, is it the same as:
> https://syzkaller.appspot.com/bug?id=f6450554481c55c131cc23d581fbd8ea42e63e18
> If so, is it possible to make KASAN detect this consistently with the
> same crash type so that syzbot does not report duplicates?

It looks like both of these occur immediately after failure injection. I
think my assumption that I could ignore the chance of failures in the
per-cpu allocation path will have to be revisited. That's annoying.

I'll try to spin something today but Andrey feel free to pip me at the
post again :)

I'm not 100% confident to call them dups just yet, but I'm about 80%
confident that they are.

Regards,
Daniel
>
>> RDX: 000000000000003c RSI: 0000000020000080 RDI: 0c00000000000000
>> RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000018
>> R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000000
>> BUG: unable to handle page fault for address: fffff91ffff00000
>> #PF: supervisor read access in kernel mode
>> #PF: error_code(0x0000) - not-present page
>> PGD 21ffe6067 P4D 21ffe6067 PUD aa56c067 PMD aa56d067 PTE 0
>> Oops: 0000 [#1] PREEMPT SMP KASAN
>> CPU: 1 PID: 8999 Comm: syz-executor865 Not tainted
>> 5.4.0-next-20191203-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
>> RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
>> RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
>> RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
>> RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
>> Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e
>> 8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74
>> ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
>> RSP: 0018:ffffc90001f67a80 EFLAGS: 00010216
>> RAX: fffff91ffff00000 RBX: fffff91ffff01000 RCX: ffffffff819e1589
>> RDX: 0000000000000001 RSI: 0000000000008000 RDI: ffffe8ffff800000
>> RBP: ffffc90001f67a98 R08: fffff91ffff01000 R09: 0000000000001000
>> R10: fffff91ffff00fff R11: ffffe8ffff807fff R12: fffff91ffff00000
>> R13: 0000000000008000 R14: 0000000000000000 R15: ffff88821fffd100
>> FS:  00000000011a7880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: fffff91ffff00000 CR3: 00000000a94ad000 CR4: 00000000001406e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>   memset+0x24/0x40 mm/kasan/common.c:107
>>   memset include/linux/string.h:410 [inline]
>>   pcpu_alloc+0x589/0x1380 mm/percpu.c:1734
>>   __alloc_percpu_gfp+0x28/0x30 mm/percpu.c:1783
>>   bpf_array_alloc_percpu kernel/bpf/arraymap.c:35 [inline]
>>   array_map_alloc+0x698/0x7d0 kernel/bpf/arraymap.c:159
>>   find_and_alloc_map kernel/bpf/syscall.c:123 [inline]
>>   map_create kernel/bpf/syscall.c:654 [inline]
>>   __do_sys_bpf+0x478/0x3810 kernel/bpf/syscall.c:3012
>>   __se_sys_bpf kernel/bpf/syscall.c:2989 [inline]
>>   __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:2989
>>   do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
>>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x442f99
>> Code: e8 ec 09 03 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7
>> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
>> ff 0f 83 cb 08 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007ffc8aa156d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
>> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000442f99
>> RDX: 000000000000003c RSI: 0000000020000080 RDI: 0c00000000000000
>> RBP: 0000000000000000 R08: 0000000000000002 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000018
>> R13: 0000000000000004 R14: 0000000000000005 R15: 0000000000000000
>> Modules linked in:
>> CR2: fffff91ffff00000
>> ---[ end trace 449f8b43dad6ffb8 ]---
>> RIP: 0010:memory_is_nonzero mm/kasan/generic.c:121 [inline]
>> RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:135 [inline]
>> RIP: 0010:memory_is_poisoned mm/kasan/generic.c:166 [inline]
>> RIP: 0010:check_memory_region_inline mm/kasan/generic.c:182 [inline]
>> RIP: 0010:check_memory_region+0x9c/0x1a0 mm/kasan/generic.c:192
>> Code: c9 4d 0f 49 c1 49 c1 f8 03 45 85 c0 0f 84 10 01 00 00 41 83 e8 01 4e
>> 8d 44 c0 08 eb 0d 48 83 c0 08 4c 39 c0 0f 84 a7 00 00 00 <48> 83 38 00 74
>> ed 4c 8d 40 08 eb 09 48 83 c0 01 49 39 c0 74 53 80
>> RSP: 0018:ffffc90001f67a80 EFLAGS: 00010216
>> RAX: fffff91ffff00000 RBX: fffff91ffff01000 RCX: ffffffff819e1589
>> RDX: 0000000000000001 RSI: 0000000000008000 RDI: ffffe8ffff800000
>> RBP: ffffc90001f67a98 R08: fffff91ffff01000 R09: 0000000000001000
>> R10: fffff91ffff00fff R11: ffffe8ffff807fff R12: fffff91ffff00000
>> R13: 0000000000008000 R14: 0000000000000000 R15: ffff88821fffd100
>> FS:  00000000011a7880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: fffff91ffff00000 CR3: 00000000a94ad000 CR4: 00000000001406e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>
>>
>> ---
>> This bug is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@googlegroups.com.
>>
>> syzbot will keep track of this bug report. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>> syzbot can test patches for this bug, for details see:
>> https://goo.gl/tpsmEJ#testing-patches
>>
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