[PATCH v3] crypto: Use struct_size() helper in kmalloc()

[PATCH v3] crypto: Use struct_size() helper in kmalloc()

[GUO Zihua]

Make use of struct_size() helper for structures containing flexible array
member instead of sizeof() which prevents potential issues, as well as
increase readability.

Reference: https://lore.kernel.org/all/CAHk-=wiGWjxs7EVUpccZEi6esvjpHJdgHQ=vtUeJ5crL62hx9A@mail.gmail.com/

Signed-off-by: GUO Zihua <guozihua@huawei.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

---

v3:
    Update commit message according to Gustavo's review.
v2:
    Use size_add() helper following Kees Cook's suggestion.
---
 crypto/asymmetric_keys/asymmetric_type.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crypto/asymmetric_keys/asymmetric_type.c b/crypto/asymmetric_keys/asymmetric_type.c
index 41a2f0eb4ce4..e020222b1fe5 100644
--- a/crypto/asymmetric_keys/asymmetric_type.c
+++ b/crypto/asymmetric_keys/asymmetric_type.c
@@ -152,7 +152,7 @@ struct asymmetric_key_id *asymmetric_key_generate_id(const void *val_1,
 {
 	struct asymmetric_key_id *kid;
 
-	kid = kmalloc(sizeof(struct asymmetric_key_id) + len_1 + len_2,
+	kid = kmalloc(struct_size(kid, data, size_add(len_1, len_2)),
 		      GFP_KERNEL);
 	if (!kid)
 		return ERR_PTR(-ENOMEM);
@@ -244,7 +244,7 @@ struct asymmetric_key_id *asymmetric_key_hex_to_key_id(const char *id)
 	if (asciihexlen & 1)
 		return ERR_PTR(-EINVAL);
 
-	match_id = kmalloc(sizeof(struct asymmetric_key_id) + asciihexlen / 2,
+	match_id = kmalloc(struct_size(match_id, data, asciihexlen / 2),
 			   GFP_KERNEL);
 	if (!match_id)
 		return ERR_PTR(-ENOMEM);
-- 
2.36.0

Re: [PATCH v3] crypto: Use struct_size() helper in kmalloc()

[Kees Cook]

On Wed, May 18, 2022 at 02:25:18PM +0800, GUO Zihua wrote:
> Make use of struct_size() helper for structures containing flexible array
> member instead of sizeof() which prevents potential issues, as well as
> increase readability.
> 
> Reference: https://lore.kernel.org/all/CAHk-=wiGWjxs7EVUpccZEi6esvjpHJdgHQ=vtUeJ5crL62hx9A@mail.gmail.com/
> 
> Signed-off-by: GUO Zihua <guozihua@huawei.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook