ASoC: sigmadsp: Add __counted_by for struct sigmadsp_data and use struct_size()

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@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/ZSRvh1j2MVVhuOUv@work
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/codecs/sigmadsp.c b/sound/soc/codecs/sigmadsp.c
index b93c078a804080b24e97e7d8603aac04e6daf3f2..56546e2394aba13736bbeb766894289e6a88d640 100644 (file)
--- 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);
                if (!data)
                        return -ENOMEM;