[PATCH 19/21] dmaengine: uniphier-xdmac: Annotate struct uniphier_xdmac_desc with __counted_by

Kees Cook
2023-08-18T00:09:44Z

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 uniphier_xdmac_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: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: dmaengine@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/dma/uniphier-xdmac.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/uniphier-xdmac.c b/drivers/dma/uniphier-xdmac.c
index 290836b7e1be..dd51522879a7 100644
--- a/drivers/dma/uniphier-xdmac.c
+++ b/drivers/dma/uniphier-xdmac.c
@@ -80,7 +80,7 @@ struct uniphier_xdmac_desc {
unsigned int nr_node;
unsigned int cur_node;
enum dma_transfer_direction dir;
- struct uniphier_xdmac_desc_node nodes[];
+ struct uniphier_xdmac_desc_node nodes[] __counted_by(nr_node);
};

struct uniphier_xdmac_chan {
@@ -295,6 +295,7 @@ uniphier_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst,
xd = kzalloc(struct_size(xd, nodes, nr), GFP_NOWAIT);
if (!xd)
return NULL;
+ xd->nr_node = nr;

for (i = 0; i < nr; i++) {
burst_size = min_t(size_t, len, XDMAC_MAX_WORD_SIZE);
@@ -309,7 +310,6 @@ uniphier_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst,
}

xd->dir = DMA_MEM_TO_MEM;
- xd->nr_node = nr;
xd->cur_node = 0;

return vchan_tx_prep(vc, &xd->vd, flags);
@@ -351,6 +351,7 @@ uniphier_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
xd = kzalloc(struct_size(xd, nodes, sg_len), GFP_NOWAIT);
if (!xd)
return NULL;
+ xd->nr_node = sg_len;

for_each_sg(sgl, sg, sg_len, i) {
xd->nodes[i].src = (direction == DMA_DEV_TO_MEM)
@@ -385,7 +386,6 @@ uniphier_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
}

xd->dir = direction;
- xd->nr_node = sg_len;
xd->cur_node = 0;

return vchan_tx_prep(vc, &xd->vd, flags);
--
2.34.1