6.1-stable review patch. If anyone has any objections, please let me know.
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From: Furong Xu 0x1207@gmail.com
[ Upstream commit 66600fac7a984dea4ae095411f644770b2561ede ]
In case the non-paged data of a SKB carries protocol header and protocol payload to be transmitted on a certain platform that the DMA AXI address width is configured to 40-bit/48-bit, or the size of the non-paged data is bigger than TSO_MAX_BUFF_SIZE on a certain platform that the DMA AXI address width is configured to 32-bit, then this SKB requires at least two DMA transmit descriptors to serve it.
For example, three descriptors are allocated to split one DMA buffer mapped from one piece of non-paged data: dma_desc[N + 0], dma_desc[N + 1], dma_desc[N + 2]. Then three elements of tx_q->tx_skbuff_dma[] will be allocated to hold extra information to be reused in stmmac_tx_clean(): tx_q->tx_skbuff_dma[N + 0], tx_q->tx_skbuff_dma[N + 1], tx_q->tx_skbuff_dma[N + 2]. Now we focus on tx_q->tx_skbuff_dma[entry].buf, which is the DMA buffer address returned by DMA mapping call. stmmac_tx_clean() will try to unmap the DMA buffer _ONLY_IF_ tx_q->tx_skbuff_dma[entry].buf is a valid buffer address.
The expected behavior that saves DMA buffer address of this non-paged data to tx_q->tx_skbuff_dma[entry].buf is: tx_q->tx_skbuff_dma[N + 0].buf = NULL; tx_q->tx_skbuff_dma[N + 1].buf = NULL; tx_q->tx_skbuff_dma[N + 2].buf = dma_map_single(); Unfortunately, the current code misbehaves like this: tx_q->tx_skbuff_dma[N + 0].buf = dma_map_single(); tx_q->tx_skbuff_dma[N + 1].buf = NULL; tx_q->tx_skbuff_dma[N + 2].buf = NULL;
On the stmmac_tx_clean() side, when dma_desc[N + 0] is closed by the DMA engine, tx_q->tx_skbuff_dma[N + 0].buf is a valid buffer address obviously, then the DMA buffer will be unmapped immediately. There may be a rare case that the DMA engine does not finish the pending dma_desc[N + 1], dma_desc[N + 2] yet. Now things will go horribly wrong, DMA is going to access a unmapped/unreferenced memory region, corrupted data will be transmited or iommu fault will be triggered :(
In contrast, the for-loop that maps SKB fragments behaves perfectly as expected, and that is how the driver should do for both non-paged data and paged frags actually.
This patch corrects DMA map/unmap sequences by fixing the array index for tx_q->tx_skbuff_dma[entry].buf when assigning DMA buffer address.
Tested and verified on DWXGMAC CORE 3.20a
Reported-by: Suraj Jaiswal quic_jsuraj@quicinc.com Fixes: f748be531d70 ("stmmac: support new GMAC4") Signed-off-by: Furong Xu 0x1207@gmail.com Reviewed-by: Hariprasad Kelam hkelam@marvell.com Reviewed-by: Simon Horman horms@kernel.org Link: https://patch.msgid.link/20241021061023.2162701-1-0x1207@gmail.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- .../net/ethernet/stmicro/stmmac/stmmac_main.c | 22 ++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index 93630840309e7..045e57c444fd7 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -4183,11 +4183,6 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev) if (dma_mapping_error(priv->device, des)) goto dma_map_err;
- tx_q->tx_skbuff_dma[first_entry].buf = des; - tx_q->tx_skbuff_dma[first_entry].len = skb_headlen(skb); - tx_q->tx_skbuff_dma[first_entry].map_as_page = false; - tx_q->tx_skbuff_dma[first_entry].buf_type = STMMAC_TXBUF_T_SKB; - if (priv->dma_cap.addr64 <= 32) { first->des0 = cpu_to_le32(des);
@@ -4206,6 +4201,23 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
stmmac_tso_allocator(priv, des, tmp_pay_len, (nfrags == 0), queue);
+ /* In case two or more DMA transmit descriptors are allocated for this + * non-paged SKB data, the DMA buffer address should be saved to + * tx_q->tx_skbuff_dma[].buf corresponding to the last descriptor, + * and leave the other tx_q->tx_skbuff_dma[].buf as NULL to guarantee + * that stmmac_tx_clean() does not unmap the entire DMA buffer too early + * since the tail areas of the DMA buffer can be accessed by DMA engine + * sooner or later. + * By saving the DMA buffer address to tx_q->tx_skbuff_dma[].buf + * corresponding to the last descriptor, stmmac_tx_clean() will unmap + * this DMA buffer right after the DMA engine completely finishes the + * full buffer transmission. + */ + tx_q->tx_skbuff_dma[tx_q->cur_tx].buf = des; + tx_q->tx_skbuff_dma[tx_q->cur_tx].len = skb_headlen(skb); + tx_q->tx_skbuff_dma[tx_q->cur_tx].map_as_page = false; + tx_q->tx_skbuff_dma[tx_q->cur_tx].buf_type = STMMAC_TXBUF_T_SKB; + /* Prepare fragments */ for (i = 0; i < nfrags; i++) { const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];