Re: [PATCH v2 3/4] treewide: Use sizeof_member() macro

Kees Cook
2019-10-29T22:30:23Z

On Thu, Oct 10, 2019 at 04:50:27PM -0700, Joe Perches wrote:
> On Thu, 2019-10-10 at 16:23 -0700, Kees Cook wrote:
> > From: Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>
> >
> > Replace all the occurrences of FIELD_SIZEOF() and sizeof_field() with
> > sizeof_member() except at places where these are defined. Later patches
> > will remove the unused definitions.
> >
> > This patch is generated using following script:
> >
> > EXCLUDE_FILES="include/linux/stddef.h|include/linux/kernel.h"
> >
> > git grep -l -e "\bFIELD_SIZEOF\b" -e "\bsizeof_field\b" | while read file;
> > do
> >
> > if [[ "$file" =~ $EXCLUDE_FILES ]]; then
> > continue
> > fi
> > sed -i -e 's/\bFIELD_SIZEOF\b/sizeof_member/g' \
> > -e 's/\bsizeof_field\b/sizeof_member/g' \
> > $file;
> > done
>
> While the sed works, a cocci script would perhaps
> be better as multi line argument realignment would
> also occur.
>
> $ cat sizeof_member.cocci
> @@
> @@
>
> - FIELD_SIZEOF
> + sizeof_member
>
> @@
> @@
>
> - sizeof_field
> + sizeof_member
> $
>
> For instance, this sed produces:
>
> diff --git a/crypto/adiantum.c b/crypto/adiantum.c
> @@ -435,10 +435,10 @@ static int adiantum_init_tfm(struct crypto_skcipher *tfm)
>
> BUILD_BUG_ON(offsetofend(struct adiantum_request_ctx, u) !=
> sizeof(struct adiantum_request_ctx));
> - subreq_size = max(FIELD_SIZEOF(struct adiantum_request_ctx,
> + subreq_size = max(sizeof_member(struct adiantum_request_ctx,
> u.hash_desc) +
> crypto_shash_descsize(hash),
> - FIELD_SIZEOF(struct adiantum_request_ctx,
> + sizeof_member(struct adiantum_request_ctx,
> u.streamcipher_req) +
> crypto_skcipher_reqsize(streamcipher));
>
>
> where the cocci script produces:
>
> --- crypto/adiantum.c
> +++ /tmp/cocci-output-22881-d8186c-adiantum.c
> @@ -435,11 +435,11 @@ static int adiantum_init_tfm(struct cryp
>
> BUILD_BUG_ON(offsetofend(struct adiantum_request_ctx, u) !=
> sizeof(struct adiantum_request_ctx));
> - subreq_size = max(FIELD_SIZEOF(struct adiantum_request_ctx,
> - u.hash_desc) +
> + subreq_size = max(sizeof_member(struct adiantum_request_ctx,
> + u.hash_desc) +
> crypto_shash_descsize(hash),
> - FIELD_SIZEOF(struct adiantum_request_ctx,
> - u.streamcipher_req) +
> + sizeof_member(struct adiantum_request_ctx,
> + u.streamcipher_req) +
> crypto_skcipher_reqsize(streamcipher));
>
> crypto_skcipher_set_reqsize(tfm,

I played with this a bit, and it seems Coccinelle can get this very very
wrong:

diff -u -p a/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c
--- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/ipsec.c
@@ -87,13 +87,13 @@ static const struct rhashtable_params rh
* value is not constant during the lifetime
* of the key object.
*/
- .key_len = FIELD_SIZEOF(struct mlx5_fpga_ipsec_sa_ctx, hw_sa) -
- FIELD_SIZEOF(struct mlx5_ifc_fpga_ipsec_sa_v1, cmd),
+ .key_len = sizeof_member(struct mlx5_fpga_ipsec_sa_ctx, hw_sa) -
+ sizeof_member(struct mlx5_ifc_fpga_ipsec_sa_v1, cmd),
.key_offset = offsetof(struct mlx5_fpga_ipsec_sa_ctx, hw_sa) +
- FIELD_SIZEOF(struct mlx5_ifc_fpga_ipsec_sa_v1, cmd),
- .head_offset = offsetof(struct mlx5_fpga_ipsec_sa_ctx, hash),
- .automatic_shrinking = true,
- .min_size = 1,
+ sizeof_member(struct mlx5_ifc_fpga_ipsec_sa_v1, cmd),
+ .head_offset = offsetof(struct mlx5_fpga_ipsec_sa_ctx, hash),
+ .automatic_shrinking = true,
+ .min_size = 1,
};

struct mlx5_fpga_ipsec {

So, since the sed is faster and causes fewer problems, I'll keep it
as-is.

--
Kees Cook