[syzbot] [net?] KMSAN: uninit-value in virtio_transport_recv_pkt

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d90b0276af8f Merge tag 'hardening-v6.6-rc3' of git://git.k..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=102c8b22680000
kernel config: https://syzkaller.appspot.com/x/.config?x=6f1a4029b69273f3
dashboard link: https://syzkaller.appspot.com/bug?extid=0c8ce1da0ac31abbadcd
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=101e58ec680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17f7adb6680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/83ae10beee39/disk-d90b0276.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c231992300f6/vmlinux-d90b0276.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6377c9c2ea97/bzImage-d90b0276.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0c8ce1...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in virtio_transport_recv_pkt+0x1c42/0x2580 net/vmw_vsock/virtio_transport_common.c:1421
virtio_transport_recv_pkt+0x1c42/0x2580 net/vmw_vsock/virtio_transport_common.c:1421
vsock_loopback_work+0x3e2/0x5d0 net/vmw_vsock/vsock_loopback.c:120
process_one_work kernel/workqueue.c:2630 [inline]
process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2703
worker_thread+0xf45/0x1490 kernel/workqueue.c:2784
kthread+0x3e8/0x540 kernel/kthread.c:388
ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

Uninit was stored to memory at:
virtio_transport_space_update net/vmw_vsock/virtio_transport_common.c:1274 [inline]
virtio_transport_recv_pkt+0x1ea4/0x2580 net/vmw_vsock/virtio_transport_common.c:1415
vsock_loopback_work+0x3e2/0x5d0 net/vmw_vsock/vsock_loopback.c:120
process_one_work kernel/workqueue.c:2630 [inline]
process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2703
worker_thread+0xf45/0x1490 kernel/workqueue.c:2784
kthread+0x3e8/0x540 kernel/kthread.c:388
ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

Uninit was created at:
slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
slab_alloc_node mm/slub.c:3478 [inline]
kmem_cache_alloc_node+0x577/0xa80 mm/slub.c:3523
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:559
__alloc_skb+0x318/0x740 net/core/skbuff.c:650
alloc_skb include/linux/skbuff.h:1286 [inline]
virtio_vsock_alloc_skb include/linux/virtio_vsock.h:66 [inline]
virtio_transport_alloc_skb+0x8b/0x1170 net/vmw_vsock/virtio_transport_common.c:58
virtio_transport_reset_no_sock net/vmw_vsock/virtio_transport_common.c:957 [inline]
virtio_transport_recv_pkt+0x1531/0x2580 net/vmw_vsock/virtio_transport_common.c:1387
vsock_loopback_work+0x3e2/0x5d0 net/vmw_vsock/vsock_loopback.c:120
process_one_work kernel/workqueue.c:2630 [inline]
process_scheduled_works+0x104e/0x1e70 kernel/workqueue.c:2703
worker_thread+0xf45/0x1490 kernel/workqueue.c:2784
kthread+0x3e8/0x540 kernel/kthread.c:388
ret_from_fork+0x66/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

CPU: 0 PID: 8 Comm: kworker/0:0 Not tainted 6.6.0-rc2-syzkaller-00337-gd90b0276af8f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Workqueue: vsock-loopback vsock_loopback_work
=====================================================


---
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[Stefano Garzarella]

Shigeru Yoshida already posted a patch here:

https://lore.kernel.org/netdev/20231026150154.3...@redhat.com/

[syzbot]

> #syz test

Your commands are accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.

>

[Eric Dumazet]

Sure thing, this is why I released this syzbot report from my queue.

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+0c8ce1...@syzkaller.appspotmail.com

Tested on:

commit: 750b9588 Merge tag 'drm-fixes-2023-10-27' of git://ano..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11ce4b63680000
kernel config: https://syzkaller.appspot.com/x/.config?x=33b75fd0ce67e090

dashboard link: https://syzkaller.appspot.com/bug?extid=0c8ce1da0ac31abbadcd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=129b8f0d680000

Note: testing is done by a robot and is best-effort only.

[Stefano Garzarella]

Thanks for that ;-)

Stefano