[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+5e23b0df3b12b8b215b7@xxxxxxxxxxxxxxxxxxxxxxxxx

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


---
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@xxxxxxxxxxxxxxxx.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup