Re: [PATCH 18/21] dmaengine: ti: omap-dma: Annotate struct omap_desc with __counted_by

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On 8/17/23 17:58, Kees Cook wrote:
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 omap_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@xxxxxxxxxx>
Cc: Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx>
Cc: dmaengine@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Reviewed-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>

Thanks
--
Gustavo

---
  drivers/dma/ti/omap-dma.c | 5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
index cf96cf915c0c..11ac3fc0a52a 100644
--- a/drivers/dma/ti/omap-dma.c
+++ b/drivers/dma/ti/omap-dma.c
@@ -124,7 +124,7 @@ struct omap_desc {
  	uint32_t csdp;		/* CSDP value */
unsigned sglen;
-	struct omap_sg sg[];
+	struct omap_sg sg[] __counted_by(sglen);
  };
enum {
@@ -1005,6 +1005,7 @@ static struct dma_async_tx_descriptor *omap_dma_prep_slave_sg(
  	d = kzalloc(struct_size(d, sg, sglen), GFP_ATOMIC);
  	if (!d)
  		return NULL;
+	d->sglen = sglen;
d->dir = dir;
  	d->dev_addr = dev_addr;
@@ -1120,8 +1121,6 @@ static struct dma_async_tx_descriptor *omap_dma_prep_slave_sg(
  		}
  	}
- d->sglen = sglen;
-
  	/* Release the dma_pool entries if one allocation failed */
  	if (ll_failed) {
  		for (i = 0; i < d->sglen; i++) {



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