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

Alex Elder
2022-09-22T13:45:23Z

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@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> 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@linaro.org>

> 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;