From 2d14720beb58870b15a52b236c3ab0be0e06e915 Mon Sep 17 00:00:00 2001 From: Muhammad Bilal Date: Sun, 20 Sep 2026 00:19:37 +0500 Subject: [PATCH] net: spacemit: clear TX descriptor on fragment mapping failure 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 Reviewed-by: Vivian Wang Reviewed-by: Troy Mitchell Link: https://patch.msgid.link/20260919191937.271202-1-meatuni001@gmail.com Signed-off-by: Paolo Abeni --- 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; }