[syzbot] [kernel?] KMSAN: uninit-value in from_kgid_munged (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8b02520ec5f7 Merge tag 'iommu-fixes-v7.0-rc7' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=150aca6a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=963de479f54c6dbb
dashboard link: https://syzkaller.appspot.com/bug?extid=0bd8f2ed639fbed5667a
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3e6cff17723a/disk-8b02520e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/641668972ac5/vmlinux-8b02520e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0360371e7446/bzImage-8b02520e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0bd8f2...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in map_id_range_up_base kernel/user_namespace.c:360 [inline]
BUG: KMSAN: uninit-value in map_id_range_up kernel/user_namespace.c:391 [inline]
BUG: KMSAN: uninit-value in map_id_up kernel/user_namespace.c:406 [inline]
BUG: KMSAN: uninit-value in from_kgid kernel/user_namespace.c:512 [inline]
BUG: KMSAN: uninit-value in from_kgid_munged+0x582/0xc40 kernel/user_namespace.c:536
map_id_range_up_base kernel/user_namespace.c:360 [inline]
map_id_range_up kernel/user_namespace.c:391 [inline]
map_id_up kernel/user_namespace.c:406 [inline]
from_kgid kernel/user_namespace.c:512 [inline]
from_kgid_munged+0x582/0xc40 kernel/user_namespace.c:536
__scm_recv_common+0x2a6/0x910 net/core/scm.c:514
scm_recv_unix+0x5e/0x580 net/core/scm.c:541
__unix_dgram_recvmsg+0x14e1/0x1750 net/unix/af_unix.c:2652
unix_dgram_recvmsg+0x115/0x180 net/unix/af_unix.c:2672
sock_recvmsg_nosec net/socket.c:1078 [inline]
sock_recvmsg+0x27b/0x310 net/socket.c:1100
____sys_recvmsg+0x193/0x620 net/socket.c:2812
___sys_recvmsg+0x20b/0x850 net/socket.c:2854
__sys_recvmsg net/socket.c:2887 [inline]
__do_sys_recvmsg net/socket.c:2893 [inline]
__se_sys_recvmsg net/socket.c:2890 [inline]
__x64_sys_recvmsg+0x20e/0x3d0 net/socket.c:2890
x64_sys_call+0x35cc/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:48
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable scm created at:
__unix_dgram_recvmsg+0x4d/0x1750 net/unix/af_unix.c:2555
unix_dgram_recvmsg+0x115/0x180 net/unix/af_unix.c:2672

CPU: 1 UID: 0 PID: 5132 Comm: udevd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
=====================================================


---
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 syzk...@googlegroups.com.

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 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