Re: [PATCH] VSOCK: fix Integer Overflow in vmci_transport_recv_dgram_cb()

[Wang Liang <wangliang74@huawei.com>]

在 2025/8/5 12:17, bsdhenrymartin@gmail.com 写道:
> From: Henry Martin <bsdhenryma@tencent.com>
>
> The vulnerability is triggered when processing a malicious VMCI datagram
> with an extremely large `payload_size` value. The attack path is:
>
> 1. Attacker crafts a malicious `vmci_datagram` with `payload_size` set
>     to a value near `SIZE_MAX` (e.g., `SIZE_MAX - offsetof(struct
>     vmci_datagram, payload) + 1`)
> 2. The function calculates: `size = VMCI_DG_SIZE(dg)` Where
>     `VMCI_DG_SIZE(dg)` expands to `offsetof(struct vmci_datagram,
>     payload) + dg->payload_size`
> 3. Integer overflow occurs during this addition, making `size` smaller
>     than the actual datagram size
>
> Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
> Reported-by: TCS Robot <tcs_robot@tencent.com>
> Signed-off-by: Henry Martin <bsdhenryma@tencent.com>
> ---
>   net/vmw_vsock/vmci_transport.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
> index 7eccd6708d66..07079669dd09 100644
> --- a/net/vmw_vsock/vmci_transport.c
> +++ b/net/vmw_vsock/vmci_transport.c
> @@ -630,6 +630,10 @@ static int vmci_transport_recv_dgram_cb(void *data, struct vmci_datagram *dg)
>   	if (!vmci_transport_allow_dgram(vsk, dg->src.context))
>   		return VMCI_ERROR_NO_ACCESS;
>   
> +	/* Validate payload size to prevent integer overflow */
> +	if (dg->payload_size > SIZE_MAX - offsetof(struct vmci_datagram, payload))
> +		return VMCI_ERROR_INVALID_ARGS;
> +


The struct vmci_datagram has no member 'payload'. Your patch may trigger 
compile error.

>   	size = VMCI_DG_SIZE(dg);
>   
>   	/* Attach the packet to the socket's receive queue as an sk_buff. */