Re: [PATCH][next] staging: greybus: Add __counted_by for struct apr_rx_buf and use struct_size()

[Alex Elder]

On 10/9/23 4:52 PM, 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() helper, 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.

Looks good to me, and I like the use of struct_size().

Reviewed-by: Alex Elder <el...@linaro.org>

Signed-off-by: Gustavo A. R. Silva <gustavo...@kernel.org>
---
  drivers/staging/greybus/raw.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/greybus/raw.c b/drivers/staging/greybus/raw.c
index a00978c8e1d2..b9c6eff7cdc1 100644
--- a/drivers/staging/greybus/raw.c
+++ b/drivers/staging/greybus/raw.c
@@ -29,7 +29,7 @@ struct gb_raw {
  struct raw_data {
        struct list_head entry;
        u32 len;
-       u8 data[];
+       u8 data[] __counted_by(len);
  };

static const struct class raw_class = {

@@ -73,7 +73,7 @@ static int receive_data(struct gb_raw *raw, u32 len, u8 *data)
                goto exit;
        }

- raw_data = kmalloc(sizeof(*raw_data) + len, GFP_KERNEL);

+       raw_data = kmalloc(struct_size(raw_data, data, len), GFP_KERNEL);
        if (!raw_data) {
                retval = -ENOMEM;
                goto exit;