[PATCH AUTOSEL 5.4 2/7] usb: dwc2: gadget: Don't write invalid mapped sg entries into dma_desc with iommu enabled

Sasha Levin
2024-07-28T16:10:37Z

From: Peng Hongchi <hongchi.peng@siengine.com>

[ Upstream commit 1134289b6b93d73721340b66c310fd985385e8fa ]

When using dma_map_sg() to map the scatterlist with iommu enabled,
the entries in the scatterlist can be mergerd into less but longer
entries in the function __finalise_sg(). So that the number of
valid mapped entries is actually smaller than ureq->num_reqs,and
there are still some invalid entries in the scatterlist with
dma_addr=0xffffffff and len=0. Writing these invalid sg entries
into the dma_desc can cause a data transmission error.

The function dma_map_sg() returns the number of valid map entries
and the return value is assigned to usb_request::num_mapped_sgs in
function usb_gadget_map_request_by_dev(). So that just write valid
mapped entries into dma_desc according to the usb_request::num_mapped_sgs,
and set the IOC bit if it's the last valid mapped entry.

This patch poses no risk to no-iommu situation, cause
ureq->num_mapped_sgs equals ureq->num_sgs while using dma_direct_map_sg()
to map the scatterlist whith iommu disabled.

Signed-off-by: Peng Hongchi <hongchi.peng@siengine.com>
Link: https://lore.kernel.org/r/20240523100315.7226-1-hongchi.peng@siengine.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/usb/dwc2/gadget.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
index b341bbc9f1dad..abc2271799e0a 100644
--- a/drivers/usb/dwc2/gadget.c
+++ b/drivers/usb/dwc2/gadget.c
@@ -885,10 +885,10 @@ static void dwc2_gadget_config_nonisoc_xfer_ddma(struct dwc2_hsotg_ep *hs_ep,
}

/* DMA sg buffer */
- for_each_sg(ureq->sg, sg, ureq->num_sgs, i) {
+ for_each_sg(ureq->sg, sg, ureq->num_mapped_sgs, i) {
dwc2_gadget_fill_nonisoc_xfer_ddma_one(hs_ep, &desc,
sg_dma_address(sg) + sg->offset, sg_dma_len(sg),
- sg_is_last(sg));
+ (i == (ureq->num_mapped_sgs - 1)));
desc_count += hs_ep->desc_count;
}

--
2.43.0