Re: KMSAN: uninit-value in bpf_iter_prog_supported

[Dmitry Vyukov]

On Sun, Feb 7, 2021 at 1:20 PM syzbot
<syzbot+580f4f2a272e452d55cb@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx

+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
> 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
> =====================================================
>
>
> ---
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