[alsa-devel] [PATCH] ASoC: wm_adsp: Fix validation of firmware and coeff lengths

[Ben Hutchings]

The checks for whether another region/block header could be present
are subtracting the size from the current offset.  Obviously we should
instead subtract the offset from the size.

The checks for whether the region/block data fit in the file are
adding the data size to the current offset and header size, without
checking for integer overflow.  Rearrange these so that overflow is
impossible.

Cc: stable at vger.kernel.org
Signed-off-by: Ben Hutchings <ben.hutchings at codethink.co.uk>
---
 sound/soc/codecs/wm_adsp.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/sound/soc/codecs/wm_adsp.c b/sound/soc/codecs/wm_adsp.c
index 65c059b5ffd7..66e32f5d2917 100644
--- a/sound/soc/codecs/wm_adsp.c
+++ b/sound/soc/codecs/wm_adsp.c
@@ -1733,7 +1733,7 @@ static int wm_adsp_load(struct wm_adsp *dsp)
 		 le64_to_cpu(footer->timestamp));
 
 	while (pos < firmware->size &&
-	       pos - firmware->size > sizeof(*region)) {
+	       sizeof(*region) < firmware->size - pos) {
 		region = (void *)&(firmware->data[pos]);
 		region_name = "Unknown";
 		reg = 0;
@@ -1782,8 +1782,8 @@ static int wm_adsp_load(struct wm_adsp *dsp)
 			 regions, le32_to_cpu(region->len), offset,
 			 region_name);
 
-		if ((pos + le32_to_cpu(region->len) + sizeof(*region)) >
-		    firmware->size) {
+		if (le32_to_cpu(region->len) >
+		    firmware->size - pos - sizeof(*region)) {
 			adsp_err(dsp,
 				 "%s.%d: %s region len %d bytes exceeds file length %zu\n",
 				 file, regions, region_name,
@@ -2253,7 +2253,7 @@ static int wm_adsp_load_coeff(struct wm_adsp *dsp)
 
 	blocks = 0;
 	while (pos < firmware->size &&
-	       pos - firmware->size > sizeof(*blk)) {
+	       sizeof(*blk) < firmware->size - pos) {
 		blk = (void *)(&firmware->data[pos]);
 
 		type = le16_to_cpu(blk->type);
@@ -2327,8 +2327,8 @@ static int wm_adsp_load_coeff(struct wm_adsp *dsp)
 		}
 
 		if (reg) {
-			if ((pos + le32_to_cpu(blk->len) + sizeof(*blk)) >
-			    firmware->size) {
+			if (le32_to_cpu(blk->len) >
+			    firmware->size - pos - sizeof(*blk)) {
 				adsp_err(dsp,
 					 "%s.%d: %s region len %d bytes exceeds file length %zu\n",
 					 file, blocks, region_name,
-- 
2.15.0.rc0