[PATCH v3 net] vsock: fix buffer size clamping order

[PATCH v3 net] vsock: fix buffer size clamping order

[Norbert Szetei]

In vsock_update_buffer_size(), the buffer size was being clamped to the
maximum first, and then to the minimum. If a user sets a minimum buffer
size larger than the maximum, the minimum check overrides the maximum
check, inverting the constraint.

This breaks the intended socket memory boundaries by allowing the
vsk->buffer_size to grow beyond the configured vsk->buffer_max_size.

Fix this by checking the minimum first, and then the maximum. This
ensures the buffer size never exceeds the buffer_max_size.

Fixes: b9f2b0ffde0c ("vsock: handle buffer_size sockopts in the core")
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Norbert Szetei <norbert@doyensec.com>
---
v3: 
 - Added Fixes and Suggested-by tags.

 net/vmw_vsock/af_vsock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index d912ed2f012a..08f4dfb9782c 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1951,12 +1951,12 @@ static void vsock_update_buffer_size(struct vsock_sock *vsk,
 				     const struct vsock_transport *transport,
 				     u64 val)
 {
-	if (val > vsk->buffer_max_size)
-		val = vsk->buffer_max_size;
-
 	if (val < vsk->buffer_min_size)
 		val = vsk->buffer_min_size;
 
+	if (val > vsk->buffer_max_size)
+		val = vsk->buffer_max_size;
+
 	if (val != vsk->buffer_size &&
 	    transport && transport->notify_buffer_size)
 		transport->notify_buffer_size(vsk, &val);
-- 
2.53.0

Re: [PATCH v3 net] vsock: fix buffer size clamping order

[Stefano Garzarella]

On Thu, Apr 09, 2026 at 06:34:12PM +0200, Norbert Szetei wrote:
>In vsock_update_buffer_size(), the buffer size was being clamped to the
>maximum first, and then to the minimum. If a user sets a minimum buffer
>size larger than the maximum, the minimum check overrides the maximum
>check, inverting the constraint.
>
>This breaks the intended socket memory boundaries by allowing the
>vsk->buffer_size to grow beyond the configured vsk->buffer_max_size.
>
>Fix this by checking the minimum first, and then the maximum. This
>ensures the buffer size never exceeds the buffer_max_size.
>
>Fixes: b9f2b0ffde0c ("vsock: handle buffer_size sockopts in the core")
>Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
>Signed-off-by: Norbert Szetei <norbert@doyensec.com>
>---
>v3:
> - Added Fixes and Suggested-by tags.
>
> net/vmw_vsock/af_vsock.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)

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