dmaengine: ti: omap-dma: Annotate struct omap_desc with __counted_by

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@kernel.org>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230817235859.49846-18-keescook@chromium.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
index 76db0fc19524d43fec5b098b088447aea96cc37e..b9e0e22383b7202ba6c81d5a79cde1a7707a419d 100644 (file)
--- 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++) {