Subject: [syzbot] [bpf?] [net?] KMSAN: uninit-value in dev_map_lookup_elem

From: syzbot <[email-masked]>
Date: Mon, 25 Mar 2024 02:36:28 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    5e74df2f8f15 Merge tag 'x86-urgent-2024-03-24' of git://gi..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=148872a5180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e6bd769cb793b98a
dashboard link: https://syzkaller.appspot.com/bug?extid=1a3cf6f08d68868f9db3
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=15921a6e180000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12e081f1180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1a82880723a7/disk-5e74df2f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fd3046ac43b9/vmlinux-5e74df2f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2097be59cbc1/bzImage-5e74df2f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

=====================================================
BUG: KMSAN: uninit-value in __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
BUG: KMSAN: uninit-value in dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
 __dev_map_lookup_elem kernel/bpf/devmap.c:441 [inline]
 dev_map_lookup_elem+0xf3/0x170 kernel/bpf/devmap.c:796
 ____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_run256+0xb5/0xe0 kernel/bpf/core.c:2237
 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_run5+0x16f/0x350 kernel/trace/bpf_trace.c:2423
 __bpf_trace_ext4_remove_blocks+0x45/0x60 include/trace/events/ext4.h:1984
 __traceiter_ext4_remove_blocks+0xb5/0x170 include/trace/events/ext4.h:1984
 trace_ext4_remove_blocks include/trace/events/ext4.h:1984 [inline]
 ext4_remove_blocks fs/ext4/extents.c:2463 [inline]
 ext4_ext_rm_leaf fs/ext4/extents.c:2686 [inline]
 ext4_ext_remove_space+0x4e30/0x7e00 fs/ext4/extents.c:2934
 ext4_ext_truncate+0x1e3/0x390 fs/ext4/extents.c:4440
 ext4_truncate+0x14c6/0x1e10 fs/ext4/inode.c:4146
 ext4_evict_inode+0x1886/0x24d0 fs/ext4/inode.c:258
 evict+0x3ae/0xa60 fs/inode.c:667
 iput_final fs/inode.c:1741 [inline]
 iput+0x9ca/0xe10 fs/inode.c:1767
 d_delete_notify include/linux/fsnotify.h:307 [inline]
 vfs_rmdir+0x53c/0x790 fs/namei.c:4222
 do_rmdir+0x630/0x8b0 fs/namei.c:4268
 __do_sys_rmdir fs/namei.c:4287 [inline]
 __se_sys_rmdir fs/namei.c:4285 [inline]
 __x64_sys_rmdir+0x78/0xb0 fs/namei.c:4285
 do_syscall_64+0xd5/0x1f0
 entry_SYSCALL_64_after_hwframe+0x6d/0x75

Local variable stack created at:
 __bpf_prog_run256+0x45/0xe0 kernel/bpf/core.c:2237
 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_run5+0x16f/0x350 kernel/trace/bpf_trace.c:2423

CPU: 0 PID: 5017 Comm: syz-executor365 Not tainted 6.8.0-syzkaller-13236-g5e74df2f8f15 #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 [email-masked].

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