5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matt Vollrath <redacted>

[ Upstream commit e94eaef11142b01f77bf8ba4d0b59720b7858109 ]

If an error is encountered while mapping TX buffers, the driver should
unmap any buffers already mapped for that skb.

Because count is incremented after a successful mapping, it will always
match the correct number of unmappings needed when dma_error is reached.
Decrementing count before the while loop in dma_error causes an
off-by-one error. If any mapping was successful before an unsuccessful
mapping, exactly one DMA mapping would leak.

In these commits, a faulty while condition caused an infinite loop in
dma_error:
Commit 03b1320dfcee ("e1000e: remove use of skb_dma_map from e1000e
driver")
Commit 602c0554d7b0 ("e1000: remove use of skb_dma_map from e1000 driver")

Commit c1fa347f20f1 ("e1000/e1000e/igb/igbvf/ixgb/ixgbe: Fix tests of
unsigned in *_tx_map()") fixed the infinite loop, but introduced the
off-by-one error.

This issue may still exist in the igbvf driver, but I did not address it
in this patch.

Fixes: c1fa347f20f1 ("e1000/e1000e/igb/igbvf/ixgb/ixgbe: Fix tests of unsigned in *_tx_map()")
Assisted-by: Claude:claude-4.6-opus
Signed-off-by: Matt Vollrath <redacted>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/intel/e1000/e1000_main.c | 2 --
 drivers/net/ethernet/intel/e1000e/netdev.c    | 2 --
 2 files changed, 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 0b75029029132..d7e7c619a98e2 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c

@@ -2951,8 +2951,6 @@ static int e1000_tx_map(struct e1000_adapter *adapter,
 dma_error:
 	dev_err(&pdev->dev, "TX DMA map failed\n");
 	buffer_info->dma = 0;
-	if (count)
-		count--;
 
 	while (count--) {
 		if (i == 0)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index b700663a634d2..902ada6a3b06c 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c

@@ -5633,8 +5633,6 @@ static int e1000_tx_map(struct e1000_ring *tx_ring, struct sk_buff *skb,
 dma_error:
 	dev_err(&pdev->dev, "Tx DMA map failed\n");
 	buffer_info->dma = 0;
-	if (count)
-		count--;
 
 	while (count--) {
 		if (i == 0)

-- 
2.51.0