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Sat, 19 Sep 2026 12:19:49 -0700 (PDT) Received: from fedora ([202.47.63.86]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48724593bbfsm8097078f8f.27.2026.09.19.12.19.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 12:19:48 -0700 (PDT) From: Muhammad Bilal To: andrew+netdev@lunn.ch Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, dlan@kernel.org, wangruikang@iscas.ac.cn, vadim.fedorenko@linux.dev, maxime.chevallier@bootlin.com, troy.mitchell@linux.spacemit.com, netdev@vger.kernel.org, linux-riscv@infradead.org, spacemit@lists.linux.dev, linux-kernel@vger.kernel.org, Muhammad Bilal Subject: [PATCH] net: spacemit: clear TX descriptor on fragment mapping failure Date: Sun, 20 Sep 2026 00:19:37 +0500 Message-ID: <20260919191937.271202-1-meatuni001@gmail.com> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: spacemit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit emac_tx_mem_map() writes TX_DESC_0_OWN into the ring descriptor for every slot beyond old_head as soon as that slot's memset()'d local copy is committed with "*tx_desc_addr = tx_desc", i.e. before the buffers for that slot have necessarily all been mapped successfully. If emac_tx_map_frag() then fails on a later fragment, the err_free_skb path calls emac_free_tx_buf() to unmap and drop the skb, but leaves the already-written descriptor memory untouched, and tx_ring->head is never advanced past old_head (the "tx_ring->head = head" store is skipped by the goto). So a slot between old_head and the rolled-back head can be left with TX_DESC_0_OWN set and buffer_addr_{1,2} pointing at DMA mappings that emac_free_tx_buf() just tore down, while software considers that slot free again. The next successful emac_tx_mem_map() call only rebuilds old_head itself; if the DMA engine auto-advances into the following descriptor once it finishes old_head's packet, it will fetch that stale, already-unmapped address. emac_tx_clean_desc() already treats emac_free_tx_buf() and clearing the descriptor as a pair when reclaiming completed descriptors; do the same in the mapping failure path. Fixes: bfec6d7f2001 ("net: spacemit: Add K1 Ethernet MAC") Signed-off-by: Muhammad Bilal --- drivers/net/ethernet/spacemit/k1_emac.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/ethernet/spacemit/k1_emac.c b/drivers/net/ethernet/spacemit/k1_emac.c index f7f16397a2c2..d641ac26a1e8 100644 --- a/drivers/net/ethernet/spacemit/k1_emac.c +++ b/drivers/net/ethernet/spacemit/k1_emac.c @@ -803,6 +803,9 @@ static void emac_tx_mem_map(struct emac_priv *priv, struct sk_buff *skb) while (i != head) { emac_free_tx_buf(priv, i); + tx_desc_addr = &((struct emac_desc *)tx_ring->desc_addr)[i]; + memset(tx_desc_addr, 0, sizeof(*tx_desc_addr)); + if (++i == tx_ring->total_cnt) i = 0; } -- 2.55.0