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Date: Mon, 6 Nov 2023 09:42:56 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Shigeru Yoshida <syoshida@...hat.com>
Cc: stefanha@...hat.com, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, kvm@...r.kernel.org, 
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzbot+0c8ce1da0ac31abbadcd@...kaller.appspotmail.com
Subject: Re: [PATCH net v2] virtio/vsock: Fix uninit-value in
 virtio_transport_recv_pkt()

On Sun, Nov 05, 2023 at 12:05:31AM +0900, Shigeru Yoshida wrote:
>KMSAN reported the following uninit-value access issue:
>
>=====================================================
>BUG: KMSAN: uninit-value in virtio_transport_recv_pkt+0x1dfb/0x26a0 net/vmw_vsock/virtio_transport_common.c:1421
> virtio_transport_recv_pkt+0x1dfb/0x26a0 net/vmw_vsock/virtio_transport_common.c:1421
> vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120
> process_one_work kernel/workqueue.c:2630 [inline]
> process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703
> worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784
> kthread+0x3cc/0x520 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+0x1ee8/0x26a0 net/vmw_vsock/virtio_transport_common.c:1415
> vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120
> process_one_work kernel/workqueue.c:2630 [inline]
> process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703
> worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784
> kthread+0x3cc/0x520 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+0x105/0xad0 mm/slab.h:767
> slab_alloc_node mm/slub.c:3478 [inline]
> kmem_cache_alloc_node+0x5a2/0xaf0 mm/slub.c:3523
> kmalloc_reserve+0x13c/0x4a0 net/core/skbuff.c:559
> __alloc_skb+0x2fd/0x770 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+0x90/0x11e0 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+0x1279/0x26a0 net/vmw_vsock/virtio_transport_common.c:1387
> vsock_loopback_work+0x3bb/0x5a0 net/vmw_vsock/vsock_loopback.c:120
> process_one_work kernel/workqueue.c:2630 [inline]
> process_scheduled_works+0xff6/0x1e60 kernel/workqueue.c:2703
> worker_thread+0xeca/0x14d0 kernel/workqueue.c:2784
> kthread+0x3cc/0x520 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: 1 PID: 10664 Comm: kworker/1:5 Not tainted 6.6.0-rc3-00146-g9f3ebbef746f #3
>Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc38 04/01/2014
>Workqueue: vsock-loopback vsock_loopback_work
>=====================================================
>
>The following simple reproducer can cause the issue described above:
>
>int main(void)
>{
>  int sock;
>  struct sockaddr_vm addr = {
>    .svm_family = AF_VSOCK,
>    .svm_cid = VMADDR_CID_ANY,
>    .svm_port = 1234,
>  };
>
>  sock = socket(AF_VSOCK, SOCK_STREAM, 0);
>  connect(sock, (struct sockaddr *)&addr, sizeof(addr));
>  return 0;
>}
>
>This issue occurs because the `buf_alloc` and `fwd_cnt` fields of the
>`struct virtio_vsock_hdr` are not initialized when a new skb is allocated
>in `virtio_transport_init_hdr()`. This patch resolves the issue by
>initializing these fields during allocation.
>
>Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
>Reported-and-tested-by: syzbot+0c8ce1da0ac31abbadcd@...kaller.appspotmail.com
>Closes: https://syzkaller.appspot.com/bug?extid=0c8ce1da0ac31abbadcd
>Signed-off-by: Shigeru Yoshida <syoshida@...hat.com>
>---
>v1->v2:
>- Rebase on the latest net tree
>https://lore.kernel.org/all/20231026150154.3536433-1-syoshida@redhat.com/
>---
> net/vmw_vsock/virtio_transport_common.c | 2 ++
> 1 file changed, 2 insertions(+)

The patch remained the same, so you could bring back my R-b ;-)
In any case:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

Thanks,
Stefano

>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index e22c81435ef7..dc65dd4d26df 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -130,6 +130,8 @@ static void virtio_transport_init_hdr(struct sk_buff *skb,
> 	hdr->dst_port	= cpu_to_le32(dst_port);
> 	hdr->flags	= cpu_to_le32(info->flags);
> 	hdr->len	= cpu_to_le32(payload_len);
>+	hdr->buf_alloc	= cpu_to_le32(0);
>+	hdr->fwd_cnt	= cpu_to_le32(0);
> }
>
> static void virtio_transport_copy_nonlinear_skb(const struct sk_buff *skb,
>-- 
>2.41.0
>


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