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ima: Fix ima digest hash table key calculation 

Function hash_long() accepts unsigned long, while currently only one byte
is passed from ima_hash_key(), which calculates a key for ima_htable.

Given that hashing the digest does not give clear benefits compared to
using the digest itself, remove hash_long() and return the modulus
calculated on the first two bytes of the digest with the number of slots.
Also reduce the depth of the hash table by doubling the number of slots.

Cc: stable@vger.kernel.org
Fixes: 3323eec921 ("integrity: IMA as an integrity service provider")
Co-developed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Krzysztof Struczynski <krzysztof.struczynski@huawei.com>
Acked-by: David.Laight@aculab.com (big endian system concerns)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Krzysztof Struczynski 2020-04-28 09:30:10 +02:00 committed by Mimi Zohar
parent 2592677c04
commit 1129d31b55
1 changed files with 4 additions and 3 deletions
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7
security/integrity/ima/ima.h
View File

@ -36,7 +36,7 @@ enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
#define IMA_DIGEST_SIZE SHA1_DIGEST_SIZE
#define IMA_EVENT_NAME_LEN_MAX 255
#define IMA_HASH_BITS 9
#define IMA_HASH_BITS 10
#define IMA_MEASURE_HTABLE_SIZE (1 << IMA_HASH_BITS)
#define IMA_TEMPLATE_FIELD_ID_MAX_LEN 16
@ -179,9 +179,10 @@ struct ima_h_table {
};
extern struct ima_h_table ima_htable;
static inline unsigned long ima_hash_key(u8 *digest)
static inline unsigned int ima_hash_key(u8 *digest)
{
return hash_long(*digest, IMA_HASH_BITS);
/* there is no point in taking a hash of part of a digest */
return (digest[0] | digest[1] << 8) % IMA_MEASURE_HTABLE_SIZE;
}
#define __ima_hooks(hook) \