On Mon, Apr 06, 2026 at 08:36:16PM +0200, Norbert Szetei wrote:
Hi Stefano,
I like option 1 the most, as it is the most straightforward way to fix
the issue. I am including the patch below. This fixes the clamping
mismatch, but as you pointed out, it won't solve the root problem
regarding the issue to arbitrarily set a maximum buffer value.
Since VSOCK uses a unified buffer size rather than separating read and
write buffers like the core stack, introducing a vsock-specific sysctl
(e.g., net.vmw_vsock.buffer_max_size) seems the cleanest approach to me.
I was also considering net.core.wmem_max/rmem_max, but mapping to those
feels less natural.
I would prefer to stop to add custom sysctl/sockopt for vsock and start
to reuse the common ones, so if net.core.wmem_max/rmem_max can be used
in some way, maybe we can try that path first and fallback to a custom
one if we see it isn't doable.
If you agree with the vsock-specific sysctl, or have a different
suggestion, let me know and I will send a follow-up patch for that.
Thanks.
Best, Norbert
-- >8 --
From f5d160167c862c7f2ad6e6a1d4181d01997b683a Mon Sep 17 00:00:00 2001
From: Norbert Szetei <[email protected]>
Date: Mon, 6 Apr 2026 19:52:52 +0200
Subject: [PATCH] vsock: fix buffer size clamping order
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.
Please add a Fixes tag here, that should be:
Fixes: b9f2b0ffde0c ("vsock: handle buffer_size sockopts in the core")
For virtio transport it was pre-existing of that commit IIUC, but
doesn't metter since these changes will not apply without that commit,
so should be fine.
Please add also a Suggested-by.
Signed-off-by: Norbert Szetei <[email protected]>
---
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;
+
The patch itself LGTM!
Thanks,
Stefano
