Re: [PATCH 3/5] ima: Fix ima digest hash table key calculation
From: Mimi Zohar
Date: Wed Apr 22 2020 - 16:56:38 EST
Hi Roberto, Krsysztof,
On Wed, 2020-03-25 at 17:11 +0100, Roberto Sassu wrote:
> From: Krzysztof Struczynski <krzysztof.struczynski@xxxxxxxxxx>
>
> Function hash_long() accepts unsigned long, while currently only one byte
> is passed from ima_hash_key(), which calculates a key for ima_htable. Use
> more bytes to avoid frequent collisions.
>
> Length of the buffer is not explicitly passed as a function parameter,
> because this function expects a digest whose length is greater than the
> size of unsigned long.
Somehow I missed the original report of this problemÂhttps://lore.kern
el.org/patchwork/patch/674684/. ÂThis patch is definitely better, but
how many unique keys are actually being used? ÂIs it anywhere near
IMA_MEASURE_HTABLE_SIZE(512)?
Do we need a new securityfs entry to display the number used?
Mimi
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 3323eec921ef ("integrity: IMA as an integrity service provider")
> Signed-off-by: Krzysztof Struczynski <krzysztof.struczynski@xxxxxxxxxx>
> ---
> security/integrity/ima/ima.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 64317d95363e..cf0022c2bc14 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -177,7 +177,7 @@ extern struct ima_h_table ima_htable;
>
> static inline unsigned long ima_hash_key(u8 *digest)
> {
> - return hash_long(*digest, IMA_HASH_BITS);
> + return hash_long(*((unsigned long *)digest), IMA_HASH_BITS);
> }
>
> #define __ima_hooks(hook) \