2022-05-18 03:25:39

by GUO Zihua

Subject: [PATCH v2] crypto: Use struct_size() helper in kmalloc()

Make use of struct_size() heler for structures containing flexible array
member instead of sizeof() which prevents potential issues as well as
addressing the following sparse warning:

crypto/asymmetric_keys/asymmetric_type.c:155:23: warning: using sizeof
on a flexible structure
crypto/asymmetric_keys/asymmetric_type.c:247:28: warning: using sizeof
on a flexible structure

Reference: https://github.com/KSPP/linux/issues/174

Signed-off-by: GUO Zihua <[email protected]>

---

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

2022-05-18 05:24:41

by Gustavo A. R. Silva

Subject: Re: [PATCH v2] crypto: Use struct_size() helper in kmalloc()

On Wed, May 18, 2022 at 08:56:39AM +0800, GUO Zihua wrote:
> Make use of struct_size() heler for structures containing flexible array
> member instead of sizeof() which prevents potential issues as well as
> addressing the following sparse warning:
>
> crypto/asymmetric_keys/asymmetric_type.c:155:23: warning: using sizeof
> on a flexible structure
> crypto/asymmetric_keys/asymmetric_type.c:247:28: warning: using sizeof
> on a flexible structure

The warnings above are not silenced with this patch as struct_size()
internally use sizeof on the struct-with-flex-array.

However, the use of struct_size() instead of the open-coded expressions
in the calls to kmalloc() is correct.

>
> Reference: https://github.com/KSPP/linux/issues/174

I updated this issue on the issue tracker. Please, from now on, just
use that issue as a list of potential open-coded instances to be
audited. :)

>
> Signed-off-by: GUO Zihua <[email protected]>

Reviewed-by: Gustavo A. R. Silva <[email protected]>

Thanks
--
Gustavo

>
> ---
>
> 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
>