Subject: [PATCH v3] net: ipa: Proactively round up to kmalloc bucket size

From: Kees Cook <[email-masked]>
Date: Tue, 18 Oct 2022 02:28:27 -0700

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" <[email-masked]>
Cc: Eric Dumazet <[email-masked]>
Cc: Jakub Kicinski <[email-masked]>
Cc: Paolo Abeni <[email-masked]>
Cc: [email-masked]
Reviewed-by: Alex Elder <[email-masked]>
Link: https://lore.kernel.org/lkml/[email-masked]
Signed-off-by: Kees Cook <[email-masked]>
---
v3: rebase to v6.1-rc1
v2: https://lore.kernel.org/lkml/[email-masked]/
---
 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 26b7f683a3e1..0f52c068c46d 100644
--- a/drivers/net/ipa/gsi_trans.c
+++ b/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;
-- 
2.34.1