linux-kernel - KMSAN: uninit-value in bpf_iter_prog

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Message-ID: <000000000000364d5505babe13f5@google.com>
Date:   Sun, 07 Feb 2021 04:20:12 -0800
From:   syzbot <syzbot+580f4f2a272e452d55cb@...kaller.appspotmail.com>
To:     glider@...gle.com, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: KMSAN: uninit-value in bpf_iter_prog_supported

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@...kaller.appspotmail.com

=====================================================
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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