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Mon, 09 Nov 2026 15:57:14 -0800 (PST) Received: from localhost.localdomain ([2a13:e746:396c:c600::8fa]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c504a56b772sm33725066b.16.2026.11.09.15.57.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Nov 2026 15:57:13 -0800 (PST) From: "Kordian Chmielewski (mlody1212)" To: netdev@vger.kernel.org Cc: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= , bcm-kernel-feedback-list@broadcom.com, Andrew Lunn , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: [PATCH net 7/7] net: bcm4908_enet: drop RX frames longer than the buffer Date: Tue, 10 Nov 2026 00:57:00 +0100 Message-ID: <20261109235700.2586821-8-kudzo51@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261109235700.2586821-1-kudzo51@gmail.com> References: <20261109235700.2586821-1-kudzo51@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit poll_rx() takes the frame length from the DMA descriptor and passes it to skb_put() unchecked, so a length larger than the buffer ends in skb_over_panic() from the NAPI poll. It was seen on a BCM4908 with the RX channel's MAX_BURST raised to 32, where the DMA reported a length of 3388 bytes, more than twice the size of the buffer; with the default burst length it has not been seen. Drop such a frame like any other bad one and count it as a length error. Fixes: 4feffeadbcb2 ("net: broadcom: bcm4908enet: add BCM4908 controller driver") Signed-off-by: Kordian Chmielewski (mlody1212) --- drivers/net/ethernet/broadcom/bcm4908_enet.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/broadcom/bcm4908_enet.c b/drivers/net/ethernet/broadcom/bcm4908_enet.c index ea4a9eb98..b2debdfa0 100644 --- a/drivers/net/ethernet/broadcom/bcm4908_enet.c +++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c @@ -660,10 +660,13 @@ static int bcm4908_enet_poll_rx(struct napi_struct *napi, int weight) len = (ctl & DMA_CTL_LEN_DESC_BUFLENGTH) >> DMA_CTL_LEN_DESC_BUFLENGTH_SHIFT; - if (len < ETH_ZLEN || + /* A length past the buffer would make skb_put() panic the kernel */ + if (len < ETH_ZLEN || len > ENET_RX_BUF_DMA_SIZE || (ctl & (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) != (DMA_CTL_STATUS_SOP | DMA_CTL_STATUS_EOP)) { dma_unmap_single(dev, slot.dma_addr, ENET_RX_BUF_DMA_SIZE, DMA_FROM_DEVICE); skb_free_frag(slot.buf); + if (len > ENET_RX_BUF_DMA_SIZE) + enet->netdev->stats.rx_length_errors++; enet->netdev->stats.rx_dropped++; break; } -- 2.56.0