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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Felix Fietkau , linux-kernel@vger.kernel.org (open list) Subject: [PATCH net] net: bgmac: clear TX slots when freeing the ring Date: Sat, 10 Oct 2026 00:04:18 -0700 Message-ID: <20261010070418.84457-1-rosenp@gmail.com> X-Mailer: git-send-email 2.56.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit bgmac_dma_tx_ring_free() frees the skbs of pending TX slots but leaves slot->skb and slot->dma_addr set. The slots survive a down/up cycle, and bgmac_dma_tx_add() only sets slot->skb on the last slot of a packet. If a slot with a stale pointer is later used for the head or a fragment of a scatter/gather packet, bgmac_dma_tx_free() frees the old skb a second time when that slot completes. The function also picks dma_unmap_single() or dma_unmap_page() by looking at slot->skb, which is set on the last slot of a packet, while the head was mapped with dma_map_single() and the fragments with skb_frag_dma_map(). Use the SOF flag of the descriptor instead, like bgmac_dma_tx_free() does. Unmap before freeing, and clear both fields. Fixes: 9cde94506eac ("bgmac: implement scatter/gather support") Assisted-by: LLM Signed-off-by: Rosen Penev --- drivers/net/ethernet/broadcom/bgmac.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-) diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c index ebc4b3bf6c4a..f40fde1d6bce 100644 --- a/drivers/net/ethernet/broadcom/bgmac.c +++ b/drivers/net/ethernet/broadcom/bgmac.c @@ -534,17 +534,19 @@ static void bgmac_dma_tx_ring_free(struct bgmac *bgmac, unsigned int len = ctl1 & BGMAC_DESC_CTL1_LEN; slot = &ring->slots[i]; - dev_kfree_skb(slot->skb); - if (!slot->dma_addr) - continue; + if (slot->dma_addr) { + if (le32_to_cpu(dma_desc[i].ctl0) & BGMAC_DESC_CTL0_SOF) + dma_unmap_single(dma_dev, slot->dma_addr, + len, DMA_TO_DEVICE); + else + dma_unmap_page(dma_dev, slot->dma_addr, + len, DMA_TO_DEVICE); + slot->dma_addr = 0; + } - if (slot->skb) - dma_unmap_single(dma_dev, slot->dma_addr, - len, DMA_TO_DEVICE); - else - dma_unmap_page(dma_dev, slot->dma_addr, - len, DMA_TO_DEVICE); + dev_kfree_skb(slot->skb); + slot->skb = NULL; } } -- 2.56.0