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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c8ebd433459b Merge tag 'nfsd-6.19-2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1779b222580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b3903bdf68407a14
dashboard link: https://syzkaller.appspot.com/bug?extid=b7af73b6a9490f27605c
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ee938141d22/disk-c8ebd433.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/19e1ae73de06/vmlinux-c8ebd433.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2172b115d36a/bzImage-c8ebd433.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b7af73...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in wq_node_nr_active kernel/workqueue.c:1555 [inline]
BUG: KMSAN: uninit-value in pwq_dec_nr_active kernel/workqueue.c:1930 [inline]
BUG: KMSAN: uninit-value in pwq_dec_nr_in_flight+0x14f/0x1d70 kernel/workqueue.c:1991
wq_node_nr_active kernel/workqueue.c:1555 [inline]
pwq_dec_nr_active kernel/workqueue.c:1930 [inline]
pwq_dec_nr_in_flight+0x14f/0x1d70 kernel/workqueue.c:1991
process_one_work kernel/workqueue.c:3314 [inline]
process_scheduled_works+0x171b/0x1d80 kernel/workqueue.c:3340
worker_thread+0xedf/0x1590 kernel/workqueue.c:3421
kthread+0xd5c/0xf00 kernel/kthread.c:463
ret_from_fork+0x208/0x710 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Uninit was created at:
slab_post_alloc_hook mm/slub.c:4960 [inline]
slab_alloc_node mm/slub.c:5263 [inline]
kmem_cache_alloc_node_noprof+0x9e7/0x17a0 mm/slub.c:5315
kmalloc_reserve+0x13c/0x4b0 net/core/skbuff.c:586
__alloc_skb+0x805/0x1040 net/core/skbuff.c:690
alloc_skb include/linux/skbuff.h:1383 [inline]
alloc_skb_with_frags+0xc5/0xa60 net/core/skbuff.c:6712
__virtio_vsock_alloc_skb_with_frags include/linux/virtio_vsock.h:68 [inline]
virtio_vsock_alloc_linear_skb include/linux/virtio_vsock.h:81 [inline]
virtio_vsock_alloc_skb include/linux/virtio_vsock.h:87 [inline]
virtio_transport_alloc_skb+0xcb/0x1350 net/vmw_vsock/virtio_transport_common.c:267
virtio_transport_send_pkt_info+0xaf1/0x1cd0 net/vmw_vsock/virtio_transport_common.c:390
virtio_transport_stream_enqueue net/vmw_vsock/virtio_transport_common.c:1113 [inline]
virtio_transport_seqpacket_enqueue+0x1f0/0x260 net/vmw_vsock/virtio_transport_common.c:841
vsock_connectible_sendmsg+0x1336/0x1b60 net/vmw_vsock/af_vsock.c:2158
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg+0x333/0x3d0 net/socket.c:742
____sys_sendmsg+0x863/0xcf0 net/socket.c:2592
___sys_sendmsg+0x271/0x3b0 net/socket.c:2646
__sys_sendmmsg+0x2d9/0x7c0 net/socket.c:2735
__do_sys_sendmmsg net/socket.c:2762 [inline]
__se_sys_sendmmsg net/socket.c:2759 [inline]
__x64_sys_sendmmsg+0xc6/0x150 net/socket.c:2759
x64_sys_call+0x2458/0x3e70 arch/x86/include/generated/asm/syscalls_64.h:308
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd3/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 3966 Comm: kworker/u8:22 Tainted: G W L syzkaller #0 PREEMPT(none)
Tainted: [W]=WARN, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: 0x0
(loop2)
=====================================================


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