Re: [PATCH 03/12] net: ipa: Proactively round up to kmalloc bucket size

[Alex Elder]

On 9/21/22 10:10 PM, Kees Cook wrote:
> Instead of discovering the kmalloc bucket size _after_ allocation, round
> up proactively so the allocation is explicitly made for the full size,
> allowing the compiler to correctly reason about the resulting size of
> the buffer through the existing __alloc_size() hint.
>
> Cc: Alex Elder <elder@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>   drivers/net/ipa/gsi_trans.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ipa/gsi_trans.c b/drivers/net/ipa/gsi_trans.c
> index 18e7e8c405be..cec968854dcf 100644
> --- a/drivers/net/ipa/gsi_trans.c
> +++ b/drivers/net/ipa/gsi_trans.c
> @@ -89,6 +89,7 @@ int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
>   			u32 max_alloc)
>   {
>   	void *virt;
> +	size_t allocate;

I don't care about this but the reverse Christmas tree
convention would put the "allocate" variable definition
above "virt".

Whether you fix that or not, this patch looks good to me.

Reviewed-by: Alex Elder <elder@xxxxxxxxxx>

>   	if (!size)
>   		return -EINVAL;
> @@ -104,13 +105,15 @@ int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
>   	 * If there aren't enough entries starting at the free index,
>   	 * we just allocate free entries from the beginning of the pool.
>   	 */
> -	virt = kcalloc(count + max_alloc - 1, size, GFP_KERNEL);
> +	allocate = size_mul(count + max_alloc - 1, size);
> +	allocate = kmalloc_size_roundup(allocate);
> +	virt = kzalloc(allocate, GFP_KERNEL);
>   	if (!virt)
>   		return -ENOMEM;
>   
>   	pool->base = virt;
>   	/* If the allocator gave us any extra memory, use it */
> -	pool->count = ksize(pool->base) / size;
> +	pool->count = allocate / size;
>   	pool->free = 0;
>   	pool->max_alloc = max_alloc;
>   	pool->size = size;