linux-kernel - [PATCH] VSOCK: fix Integer Overflow in vmci_transport_recv_dgram

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Message-ID: <20250805041748.1728098-1-tcs_kernel@tencent.com>
Date: Tue,  5 Aug 2025 12:17:48 +0800
From: bsdhenrymartin@...il.com
To: huntazhang@...cent.com,
	jitxie@...cent.com,
	landonsun@...cent.com,
	bryan-bt.tan@...adcom.com,
	vishnu.dasa@...adcom.com,
	bcm-kernel-feedback-list@...adcom.com,
	sgarzare@...hat.com,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	horms@...nel.org
Cc: linux-kernel@...r.kernel.org,
	virtualization@...ts.linux.dev,
	netdev@...r.kernel.org,
	Henry Martin <bsdhenryma@...cent.com>,
	TCS Robot <tcs_robot@...cent.com>
Subject: [PATCH] VSOCK: fix Integer Overflow in vmci_transport_recv_dgram_cb()

From: Henry Martin <bsdhenryma@...cent.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@...cent.com>
Signed-off-by: Henry Martin <bsdhenryma@...cent.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;
+
 	size = VMCI_DG_SIZE(dg);
 
 	/* Attach the packet to the socket's receive queue as an sk_buff. */
-- 
2.41.3