[syzbot] [bpf?] KMSAN: uninit-value in percpu_array_map_lookup_elem

[syzbot]

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+5e23b0...@syzkaller.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
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
=====================================================


---
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[Martin KaFai Lau]

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+5e23b0...@syzkaller.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