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Subject: Re: KMSAN: uninit-value in bpf_iter_prog_supported
To:     Dmitry Vyukov <dvyukov@google.com>,
        syzbot <syzbot+580f4f2a272e452d55cb@syzkaller.appspotmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>, <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
CC:     Alexander Potapenko <glider@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
References: <000000000000364d5505babe13f5@google.com>
 <CACT4Y+aDGsVkzTkQ551XUpT0Z1vuiGTubvtKne+VYjK3zX67kQ@mail.gmail.com>
From:   Yonghong Song <yhs@fb.com>
Message-ID: <2affbff0-892c-8037-72a5-e698d03019e4@fb.com>
Date:   Tue, 9 Feb 2021 08:23:15 -0800
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On 2/8/21 11:35 PM, Dmitry Vyukov wrote:
> On Sun, Feb 7, 2021 at 1:20 PM syzbot
> <syzbot+580f4f2a272e452d55cb@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    73d62e81 kmsan: random: prevent boot-time reports in _mix_..
>> git tree:       https://github.com/google/kmsan.git master
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17ac5f64d00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=df698232b2ac45c9
>> dashboard link: https://syzkaller.appspot.com/bug?extid=580f4f2a272e452d55cb
>> compiler:       Debian clang version 11.0.1-2
>> userspace arch: i386
>>
>> Unfortunately, I don't have any reproducer for this issue yet.
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+580f4f2a272e452d55cb@syzkaller.appspotmail.com
> 
> +BPF maintainers
> 
>> =====================================================
>> BUG: KMSAN: uninit-value in bpf_iter_prog_supported+0x3dd/0x6a0 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/bpf_iter.c:329

I will take a look. Thanks.

>> CPU: 0 PID: 18494 Comm: bpf_preload Not tainted 5.10.0-rc4-syzkaller #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>> Call Trace:
>>   __dump_stack syzkaller/managers/upstream-kmsan-gce-386/kernel/lib/dump_stack.c:77 [inline]
>>   dump_stack+0x21c/0x280 syzkaller/managers/upstream-kmsan-gce-386/kernel/lib/dump_stack.c:118
>>   kmsan_report+0xfb/0x1e0 syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/kmsan/kmsan_report.c:118
>>   __msan_warning+0x5f/0xa0 syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/kmsan/kmsan_instr.c:197
>>   bpf_iter_prog_supported+0x3dd/0x6a0 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/bpf_iter.c:329
>>   check_attach_btf_id syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/verifier.c:11772 [inline]
>>   bpf_check+0x11872/0x1c380 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/verifier.c:11900
>>   bpf_prog_load syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/syscall.c:2210 [inline]
>>   __do_sys_bpf+0x17483/0x1aee0 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/syscall.c:4399
>>   __se_sys_bpf+0x8e/0xa0 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/syscall.c:4357
>>   __x64_sys_bpf+0x4a/0x70 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/syscall.c:4357
>>   do_syscall_64+0x9f/0x140 syzkaller/managers/upstream-kmsan-gce-386/kernel/arch/x86/entry/common.c:48
>>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> RIP: 0033:0x7fb70b5ab469
>> Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 8b 0d ff 49 2b 00 f7 d8 64 89 01 48
>> RSP: 002b:00007ffdbb4cde38 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
>> RAX: ffffffffffffffda RBX: 000000000065b110 RCX: 00007fb70b5ab469
>> RDX: 0000000000000078 RSI: 00007ffdbb4cdef0 RDI: 0000000000000005
>> RBP: 00007ffdbb4cdef0 R08: 0000001000000017 R09: 0000000000000000
>> R10: 00007ffdbb4ce0e8 R11: 0000000000000246 R12: 0000000000000000
>> R13: 00007ffdbb4cdf20 R14: 0000000000000000 R15: 0000000000000000
>>
>> Uninit was created at:
>>   kmsan_save_stack_with_flags syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/kmsan/kmsan.c:121 [inline]
>>   kmsan_internal_poison_shadow+0x5c/0xf0 syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/kmsan/kmsan.c:104
>>   kmsan_slab_alloc+0x8d/0xe0 syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/kmsan/kmsan_hooks.c:76
>>   slab_alloc_node syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/slub.c:2906 [inline]
>>   slab_alloc syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/slub.c:2915 [inline]
>>   kmem_cache_alloc_trace+0x893/0x1000 syzkaller/managers/upstream-kmsan-gce-386/kernel/mm/slub.c:2932
>>   kmalloc syzkaller/managers/upstream-kmsan-gce-386/kernel/./include/linux/slab.h:552 [inline]
>>   bpf_iter_reg_target+0x81/0x3f0 syzkaller/managers/upstream-kmsan-gce-386/kernel/kernel/bpf/bpf_iter.c:276
>>   bpf_sk_storage_map_iter_init+0x6a/0x85 syzkaller/managers/upstream-kmsan-gce-386/kernel/net/core/bpf_sk_storage.c:870
>>   do_one_initcall+0x362/0x8d0 syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1220
>>   do_initcall_level+0x1e7/0x35a syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1293
>>   do_initcalls+0x127/0x1cb syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1309
>>   do_basic_setup+0x33/0x36 syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1329
>>   kernel_init_freeable+0x238/0x38b syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1529
>>   kernel_init+0x1f/0x840 syzkaller/managers/upstream-kmsan-gce-386/kernel/init/main.c:1418
>>   ret_from_fork+0x1f/0x30 syzkaller/managers/upstream-kmsan-gce-386/kernel/arch/x86/entry/entry_64.S:296
>> =====================================================
>>
>>
>> ---
>> This report 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 issue. See:
>> https://goo.gl/tpsmEJ#status  for how to communicate with syzbot.
>>
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