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[82.53.135.12]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4908097a320sm30225605e9.3.2026.05.27.10.10.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 May 2026 10:10:48 -0700 (PDT) From: Stefano Garzarella To: netdev@vger.kernel.org Cc: "David S. Miller" , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , virtualization@lists.linux.dev, Jakub Kicinski , linux-kernel@vger.kernel.org, Xuan Zhuo , "Michael S. Tsirkin" , kvm@vger.kernel.org, Paolo Abeni , Stefano Garzarella , Jason Wang , Simon Horman , Stefan Hajnoczi , Eric Dumazet , David Laight Subject: [PATCH RESEND net] Revert "vsock/virtio: fix skb overhead overflow on 32-bit builds" Date: Wed, 27 May 2026 19:10:46 +0200 Message-ID: <20260527171046.130211-1-sgarzare@redhat.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Stefano Garzarella This reverts commit 4157501b9a8f ("vsock/virtio: fix skb overhead overflow on 32-bit builds"). The fix was semantically correct (although it would have been better to use mul_u32_u32(), as David pointed out), but in practice we are estimating the memory used to allocate the SKBs, and this will never cause a 32-bit variable to overflow on a 32-bit system, since the memory would have run out long before that. On 64-bit, SKB_TRUESIZE() already evaluates to size_t, so the multiplication is already in 64-bit arithmetic without the cast. Let's revert this to avoid unnecessary 64-bit multiplies on the per-packet receive path on 32-bit systems. Reported-by: David Laight Closes: https://lore.kernel.org/netdev/20260523173557.5cc4f4f6@pumpkin Suggested-by: "Michael S. Tsirkin" Signed-off-by: Stefano Garzarella --- net/vmw_vsock/virtio_transport_common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index b143290a311d..d4d26fba9e37 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c @@ -417,7 +417,7 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk, static bool virtio_transport_inc_rx_pkt(struct virtio_vsock_sock *vvs, u32 len) { - u64 skb_overhead = ((u64)skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0); + u64 skb_overhead = (skb_queue_len(&vvs->rx_queue) + 1) * SKB_TRUESIZE(0); /* Allow at most buf_alloc * 2 total budget (payload + overhead), * similar to how SO_RCVBUF is doubled to reserve space for sk_buff -- 2.54.0