[05/12] dma-buf: Proactively round up to kmalloc bucket size

Commit Message

Kees Cook Sept. 22, 2022, 3:10 a.m. UTC

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: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Signed-off-by: Kees Cook <[e-mail]>
---
 drivers/dma-buf/dma-resv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

Patch

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 205acb2c744d..a20f6db99b8f 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -98,12 +98,17 @@  static void dma_resv_list_set(struct dma_resv_list *list,
 static struct dma_resv_list *dma_resv_list_alloc(unsigned int max_fences)
 {
 	struct dma_resv_list *list;
+	size_t size = struct_size(list, table, max_fences);
 
-	list = kmalloc(struct_size(list, table, max_fences), GFP_KERNEL);
+	/* Round up to the next kmalloc bucket size. */
+	size = kmalloc_size_roundup(size);
+
+	list = kmalloc(size, GFP_KERNEL);
 	if (!list)
 		return NULL;
 
-	list->max_fences = (ksize(list) - offsetof(typeof(*list), table)) /
+	/* Given the resulting bucket size, recalculated max_fences. */
+	list->max_fences = (size - offsetof(typeof(*list), table)) /
 		sizeof(*list->table);
 
 	return list;