2021-01-24 14:10:58

by Stephan Müller

Subject: [PATCH v2 7/7] fs: HKDF - remove duplicate memory clearing

The clearing of the OKM memory buffer in case of an error is already
performed by the HKDF implementation crypto_hkdf_expand. Thus, the
code clearing is not needed any more in the file system code base.

Signed-off-by: Stephan Mueller <[email protected]>
---
fs/crypto/hkdf.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
index ae236b42b1f0..c48dd8ca3a46 100644
--- a/fs/crypto/hkdf.c
+++ b/fs/crypto/hkdf.c
@@ -102,13 +102,10 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
.iov_base = (u8 *)info,
.iov_len = infolen,
} };
- int err = crypto_hkdf_expand(hkdf->hmac_tfm,
- info_iov, ARRAY_SIZE(info_iov),
- okm, okmlen);

- if (unlikely(err))
- memzero_explicit(okm, okmlen); /* so caller doesn't need to */
- return err;
+ return crypto_hkdf_expand(hkdf->hmac_tfm,
+ info_iov, ARRAY_SIZE(info_iov),
+ okm, okmlen);
}

void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf)
--
2.26.2

2021-01-28 20:24:28

by Eric Biggers

Subject: Re: [PATCH v2 7/7] fs: HKDF - remove duplicate memory clearing

On Sun, Jan 24, 2021 at 03:04:50PM +0100, Stephan M?ller wrote:
> The clearing of the OKM memory buffer in case of an error is already
> performed by the HKDF implementation crypto_hkdf_expand. Thus, the
> code clearing is not needed any more in the file system code base.
>
> Signed-off-by: Stephan Mueller <[email protected]>
> ---
> fs/crypto/hkdf.c | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/fs/crypto/hkdf.c b/fs/crypto/hkdf.c
> index ae236b42b1f0..c48dd8ca3a46 100644
> --- a/fs/crypto/hkdf.c
> +++ b/fs/crypto/hkdf.c
> @@ -102,13 +102,10 @@ int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
> .iov_base = (u8 *)info,
> .iov_len = infolen,
> } };
> - int err = crypto_hkdf_expand(hkdf->hmac_tfm,
> - info_iov, ARRAY_SIZE(info_iov),
> - okm, okmlen);
>
> - if (unlikely(err))
> - memzero_explicit(okm, okmlen); /* so caller doesn't need to */
> - return err;
> + return crypto_hkdf_expand(hkdf->hmac_tfm,
> + info_iov, ARRAY_SIZE(info_iov),
> + okm, okmlen);
> }
>

Shoudn't this just be folded into the previous patch, which converted
fscrypt_hkdf_expand() to use crypto_hkdf_expand() in the first place?

- Eric