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

[syzbot <syzbot+0bd8f2ed639fbed5667a@syzkaller.appspotmail.com>]

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+0bd8f2ed639fbed5667a@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
=====================================================


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