[PATCH 08/21] dmaengine: sa11x0: Annotate struct sa11x0_dma_desc with __counted_by

Kees Cook
2023-08-18T00:00:11Z

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct sa11x0_dma_desc.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Vinod Koul <vkoul@kernel.org>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/dma/sa11x0-dma.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
index a29c13cae716..e5849622f198 100644
--- a/drivers/dma/sa11x0-dma.c
+++ b/drivers/dma/sa11x0-dma.c
@@ -78,7 +78,7 @@ struct sa11x0_dma_desc {
bool cyclic;

unsigned sglen;
- struct sa11x0_dma_sg sg[];
+ struct sa11x0_dma_sg sg[] __counted_by(sglen);
};

struct sa11x0_dma_phy;
@@ -558,6 +558,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
return NULL;
}
+ txd->sglen = j;

j = 0;
for_each_sg(sg, sgent, sglen, i) {
@@ -593,7 +594,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(

txd->ddar = c->ddar;
txd->size = size;
- txd->sglen = j;

dev_dbg(chan->device->dev, "vchan %p: txd %p: size %zu nr %u\n",
&c->vc, &txd->vd, txd->size, txd->sglen);
@@ -628,6 +628,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(
dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
return NULL;
}
+ txd->sglen = sglen;

for (i = k = 0; i < size / period; i++) {
size_t tlen, len = period;
@@ -653,7 +654,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(

txd->ddar = c->ddar;
txd->size = size;
- txd->sglen = sglen;
txd->cyclic = 1;
txd->period = sgperiod;

--
2.34.1