[PATCH v3 net 1/8] net: enetc: fix the off-by-one issue in enetc_map_tx_buffs()

Wei Fang
2025-02-24T11:30:02Z

When a DMA mapping error occurs while processing skb frags, it will free
one more tx_swbd than expected, so fix this off-by-one issue.

Fixes: d4fd0404c1c9 ("enetc: Introduce basic PF and VF ENETC ethernet drivers")
Cc: stable@vger.kernel.org
Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Suggested-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Wei Fang <wei.fang@nxp.com>
---
drivers/net/ethernet/freescale/enetc/enetc.c | 26 ++++++++++++++------
1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c b/drivers/net/ethernet/freescale/enetc/enetc.c
index 6a6fc819dfde..55ad31a5073e 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc.c
@@ -167,6 +167,24 @@ static bool enetc_skb_is_tcp(struct sk_buff *skb)
return skb->csum_offset == offsetof(struct tcphdr, check);
}

+/**
+ * enetc_unwind_tx_frame() - Unwind the DMA mappings of a multi-buffer Tx frame
+ * @tx_ring: Pointer to the Tx ring on which the buffer descriptors are located
+ * @count: Number of Tx buffer descriptors which need to be unmapped
+ * @i: Index of the last successfully mapped Tx buffer descriptor
+ */
+static void enetc_unwind_tx_frame(struct enetc_bdr *tx_ring, int count, int i)
+{
+ while (count--) {
+ struct enetc_tx_swbd *tx_swbd = &tx_ring->tx_swbd[i];
+
+ enetc_free_tx_frame(tx_ring, tx_swbd);
+ if (i == 0)
+ i = tx_ring->bd_count;
+ i--;
+ }
+}
+
static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
{
bool do_vlan, do_onestep_tstamp = false, do_twostep_tstamp = false;
@@ -372,13 +390,7 @@ static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
dma_err:
dev_err(tx_ring->dev, "DMA map error");

- do {
- tx_swbd = &tx_ring->tx_swbd[i];
- enetc_free_tx_frame(tx_ring, tx_swbd);
- if (i == 0)
- i = tx_ring->bd_count;
- i--;
- } while (count--);
+ enetc_unwind_tx_frame(tx_ring, count, i);

return 0;
}
--
2.34.1