linux-kernel - Re: [syzbot] [bpf?] KMSAN: uninit-value in percpu_array_map_lookup

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Message-ID: <fb458efd-0bc9-4a9d-aff1-e979b7abc710@linux.dev>
Date: Mon, 8 Apr 2024 22:37:21 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: syzbot <syzbot+5e23b0df3b12b8b215b7@...kaller.appspotmail.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 daniel@...earbox.net, eddyz87@...il.com, haoluo@...gle.com,
 john.fastabend@...il.com, jolsa@...nel.org, kpsingh@...nel.org,
 linux-kernel@...r.kernel.org, sdf@...gle.com, song@...nel.org,
 syzkaller-bugs@...glegroups.com, yonghong.song@...ux.dev
Subject: Re: [syzbot] [bpf?] KMSAN: uninit-value in
 percpu_array_map_lookup_elem

On 3/19/24 11:12 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    e5eb28f6d1af Merge tag 'mm-nonmm-stable-2024-03-14-09-36' ..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14e351c9180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aa3d79b689f321c8
> dashboard link: https://syzkaller.appspot.com/bug?extid=5e23b0df3b12b8b215b7
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14498006180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11e4d769180000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/eaca555a0446/disk-e5eb28f6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/4fbf90fa0d23/vmlinux-e5eb28f6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/bbae0627aafd/bzImage-e5eb28f6.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+5e23b0df3b12b8b215b7@...kaller.appspotmail.com
> 
> =====================================================
> BUG: KMSAN: uninit-value in percpu_array_map_lookup_elem+0x142/0x160 kernel/bpf/arraymap.c:243
>   percpu_array_map_lookup_elem+0x142/0x160 kernel/bpf/arraymap.c:243
>   ____bpf_map_lookup_elem kernel/bpf/helpers.c:42 [inline]
>   bpf_map_lookup_elem+0x5c/0x80 kernel/bpf/helpers.c:38
>   ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
>   __bpf_prog_run64+0xb5/0xe0 kernel/bpf/core.c:2236

#syz dup: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_lookup_elem

>   bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>   __bpf_prog_run include/linux/filter.h:657 [inline]
>   bpf_prog_run include/linux/filter.h:664 [inline]
>   __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>   bpf_trace_run3+0x132/0x320 kernel/trace/bpf_trace.c:2421
>   __bpf_trace_ext4_es_insert_delayed_block+0x34/0x50 include/trace/events/ext4.h:2481
>   trace_ext4_es_insert_delayed_block include/trace/events/ext4.h:2481 [inline]
>   ext4_es_insert_delayed_block+0x11e1/0x1290 fs/ext4/extents_status.c:2082
>   ext4_insert_delayed_block fs/ext4/inode.c:1676 [inline]
>   ext4_da_map_blocks fs/ext4/inode.c:1777 [inline]
>   ext4_da_get_block_prep+0x1714/0x1d30 fs/ext4/inode.c:1817
>   ext4_block_write_begin+0x749/0x1df0 fs/ext4/inode.c:1055
>   ext4_da_write_begin+0x889/0xec0 fs/ext4/inode.c:2894
>   generic_perform_write+0x400/0xc60 mm/filemap.c:3974
>   ext4_buffered_write_iter+0x564/0xaa0 fs/ext4/file.c:299
>   ext4_file_write_iter+0x208/0x3450
>   call_write_iter include/linux/fs.h:2108 [inline]
>   new_sync_write fs/read_write.c:497 [inline]
>   vfs_write+0xb63/0x1520 fs/read_write.c:590
>   ksys_write+0x20f/0x4c0 fs/read_write.c:643
>   __do_sys_write fs/read_write.c:655 [inline]
>   __se_sys_write fs/read_write.c:652 [inline]
>   __x64_sys_write+0x93/0xe0 fs/read_write.c:652
>   do_syscall_64+0xd5/0x1f0
>   entry_SYSCALL_64_after_hwframe+0x6d/0x75
> 
> Local variable stack created at:
>   __bpf_prog_run64+0x45/0xe0 kernel/bpf/core.c:2236
>   bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>   __bpf_prog_run include/linux/filter.h:657 [inline]
>   bpf_prog_run include/linux/filter.h:664 [inline]
>   __bpf_trace_run kernel/trace/bpf_trace.c:2381 [inline]
>   bpf_trace_run3+0x132/0x320 kernel/trace/bpf_trace.c:2421
> 
> CPU: 1 PID: 5001 Comm: syz-executor118 Not tainted 6.8.0-syzkaller-09791-ge5eb28f6d1af #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
> =====================================================