Re: [PATCH] ima: dynamically allocate shash_desc

Mimi Zohar
2019-06-17T15:56:14Z

On Mon, 2019-06-17 at 13:20 +0200, Arnd Bergmann wrote:
> On 32-bit ARM, we get a warning about excessive stack usage when
> building with clang.
>
> security/integrity/ima/ima_crypto.c:504:5: error: stack frame size
> of 1152 bytes in function 'ima_calc_field_array_hash' [-Werror,-
> Wframe-larger-than=]

I'm definitely not seeing this.  Is this problem a result of non
upstreamed patches?  For sha1, currently the only possible hash
algorithm, I'm seeing 664.

Mimi

>
> Using kmalloc to get the descriptor reduces this to 320 bytes.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> security/integrity/ima/ima_crypto.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
> index d4c7b8e1b083..8a66bab4c435 100644
> --- a/security/integrity/ima/ima_crypto.c
> +++ b/security/integrity/ima/ima_crypto.c
> @@ -461,16 +461,21 @@ static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
> struct ima_digest_data *hash,
> struct crypto_shash *tfm)
> {
> - SHASH_DESC_ON_STACK(shash, tfm);
> + struct shash_desc *shash;
> int rc, i;
>
> + shash = kmalloc(sizeof(struct shash_desc) + crypto_shash_descsize(tfm),
> + GFP_KERNEL);
> + if (!shash)
> + return -ENOMEM;
> +
> shash->tfm = tfm;
>
> hash->length = crypto_shash_digestsize(tfm);
>
> rc = crypto_shash_init(shash);
> if (rc != 0)
> - return rc;
> + goto out;
>
> for (i = 0; i < num_fields; i++) {
> u8 buffer[IMA_EVENT_NAME_LEN_MAX + 1] = { 0 };
> @@ -497,7 +502,8 @@ static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
>
> if (!rc)
> rc = crypto_shash_final(shash, hash->digest);
> -
> +out:
> + kfree(shash);
> return rc;
> }
>