On 10/10/23 00:03, Kees Cook wrote:
On Mon, Oct 09, 2023 at 03:24:23PM -0600, Gustavo A. R. Silva 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 via CONFIG_UBSAN_BOUNDS (for
array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).
While there, use struct_size() and size_sub() helpers, instead of the
open-coded version, to calculate the size for the allocation of the
whole flexible structure, including of course, the flexible-array
member.
This code was found with the help of Coccinelle, and audited and
fixed manually.
Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
---
sound/soc/codecs/sigmadsp.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/sound/soc/codecs/sigmadsp.c b/sound/soc/codecs/sigmadsp.c
index b93c078a8040..56546e2394ab 100644
--- a/sound/soc/codecs/sigmadsp.c
+++ b/sound/soc/codecs/sigmadsp.c
@@ -43,7 +43,7 @@ struct sigmadsp_data {
uint32_t samplerates;
unsigned int addr;
unsigned int length;
- uint8_t data[];
+ uint8_t data[] __counted_by(length);
};
struct sigma_fw_chunk {
@@ -270,7 +270,7 @@ static int sigma_fw_load_data(struct sigmadsp *sigmadsp,
length -= sizeof(*data_chunk);
- data = kzalloc(sizeof(*data) + length, GFP_KERNEL);
+ data = kzalloc(struct_size(data, data, length), GFP_KERNEL);
if (!data)
return -ENOMEM;
@@ -413,7 +413,8 @@ static int process_sigma_action(struct sigmadsp *sigmadsp,
if (len < 3)
return -EINVAL;
- data = kzalloc(sizeof(*data) + len - 2, GFP_KERNEL);
+ data = kzalloc(struct_size(data, data, size_sub(len, 2)),
+ GFP_KERNEL);
Since len was just size-checked before the alloc, size_sub() is a bit of
overkill, but it's not technically wrong. :P
Oops.. yep, you're right, I totally overlooked that check.
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Thanks!
--
Gustavo
