net: ipa: Proactively round up to kmalloc bucket size

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: "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
Reviewed-by: Alex Elder <elder@linaro.org>
Link: https://lore.kernel.org/lkml/4d75a9fd-1b94-7208-9de8-5a0102223e68@ieee.orgSigned-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221018092724.give.735-kees@kernel.orgSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ipa/gsi_trans.c

@@ -87,6 +87,7 @@ struct gsi_tre {
 int gsi_trans_pool_init(struct gsi_trans_pool *pool, size_t size, u32 count,
 			u32 max_alloc)
 {
+	size_t alloc_size;
 	void *virt;
 
 	if (!size)
@@ -103,13 +104,15 @@ 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);
+	alloc_size = size_mul(count + max_alloc - 1, size);
+	alloc_size = kmalloc_size_roundup(alloc_size);
+	virt = kzalloc(alloc_size, 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 = alloc_size / size;
 	pool->free = 0;
 	pool->max_alloc = max_alloc;
 	pool->size = size;