Messages in this thread | | | Date | Wed, 16 Aug 2023 10:35:56 +0200 | Subject | Re: [RFC][PATCH v2 03/13] integrity/digest_cache: Add functions to populate and search | From | Roberto Sassu <> |
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On 8/14/2023 7:13 PM, Jarkko Sakkinen wrote: > On Sat Aug 12, 2023 at 1:46 PM EEST, Roberto Sassu wrote: >> From: Roberto Sassu <roberto.sassu@huawei.com> >> >> Add digest_cache_init_htable(), to size a hash table depending on the >> number of digests to be added to the cache. >> >> Add digest_cache_add() and digest_cache_lookup() to respectively add and >> lookup a digest in the digest cache. >> >> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> >> --- >> security/integrity/digest_cache.c | 131 ++++++++++++++++++++++++++++++ >> security/integrity/digest_cache.h | 24 ++++++ >> 2 files changed, 155 insertions(+) >> >> diff --git a/security/integrity/digest_cache.c b/security/integrity/digest_cache.c >> index 4201c68171a..d14d84b804b 100644 >> --- a/security/integrity/digest_cache.c >> +++ b/security/integrity/digest_cache.c >> @@ -315,3 +315,134 @@ struct digest_cache *digest_cache_get(struct dentry *dentry, >> >> return iint->dig_user; >> } >> + >> +/** >> + * digest_cache_init_htable - Allocate and initialize the hash table >> + * @digest_cache: Digest cache >> + * @num_digests: Number of digests to add to the digest cache >> + * >> + * This function allocates and initializes the hash table. Its size is >> + * determined by the number of digests to add to the digest cache, known >> + * at this point by the parser calling this function. >> + * >> + * Return: Zero on success, a negative value otherwise. >> + */ >> +int digest_cache_init_htable(struct digest_cache *digest_cache, >> + u64 num_digests) >> +{ >> + int i; >> + >> + if (!digest_cache) >> + return 0; >> + >> + digest_cache->num_slots = num_digests / DIGEST_CACHE_HTABLE_DEPTH; >> + if (!digest_cache->num_slots) >> + digest_cache->num_slots = 1; >> + >> + digest_cache->slots = kmalloc_array(num_digests, >> + sizeof(*digest_cache->slots), >> + GFP_KERNEL); >> + if (!digest_cache->slots) >> + return -ENOMEM; >> + >> + for (i = 0; i < digest_cache->num_slots; i++) >> + INIT_HLIST_HEAD(&digest_cache->slots[i]); >> + >> + pr_debug("Initialized %d hash table slots for digest list %s\n", >> + digest_cache->num_slots, digest_cache->path_str); >> + return 0; >> +} >> + >> +/** >> + * digest_cache_add - Add a new digest to the digest cache >> + * @digest_cache: Digest cache >> + * @digest: Digest to add >> + * >> + * This function, invoked by a digest list parser, adds a digest extracted >> + * from a digest list to the digest cache. >> + * >> + * Return: Zero on success, a negative value on error. > > Nit: previous had a different phrasing "a negative value otherwise". > > I would suggest "a POSIX error code otherwise" for both.
Ok.
>> + */ >> +int digest_cache_add(struct digest_cache *digest_cache, u8 *digest) >> +{ >> + struct digest_cache_entry *entry; >> + unsigned int key; >> + int digest_len; >> + >> + if (!digest_cache) >> + return 0; >> + >> + digest_len = hash_digest_size[digest_cache->algo]; >> + >> + entry = kmalloc(sizeof(*entry) + digest_len, GFP_KERNEL); >> + if (!entry) >> + return -ENOMEM; >> + >> + memcpy(entry->digest, digest, digest_len); >> + >> + key = digest_cache_hash_key(digest, digest_cache->num_slots); >> + hlist_add_head(&entry->hnext, &digest_cache->slots[key]); >> + pr_debug("Add digest %s:%*phN from digest list %s\n", >> + hash_algo_name[digest_cache->algo], digest_len, digest, >> + digest_cache->path_str); >> + return 0; >> +} >> + >> +/** >> + * digest_cache_lookup - Searches a digest in the digest cache >> + * @digest_cache: Digest cache >> + * @digest: Digest to search >> + * @algo: Algorithm of the digest to search >> + * @pathname: Path of the file whose digest is looked up >> + * >> + * This function, invoked by IMA or EVM, searches the calculated digest of >> + * a file or file metadata in the digest cache acquired with >> + * digest_cache_get(). >> + * >> + * Return: Zero if the digest is found, a negative value if not. >> + */ >> +int digest_cache_lookup(struct digest_cache *digest_cache, u8 *digest, >> + enum hash_algo algo, const char *pathname) >> +{ >> + struct digest_cache_entry *entry; >> + unsigned int key; >> + int digest_len; >> + int search_depth = 0; >> + >> + if (!digest_cache) >> + return -ENOENT; >> + >> + if (digest_cache->algo == HASH_ALGO__LAST) { >> + pr_debug("Algorithm not set for digest list %s\n", >> + digest_cache->path_str); >> + return -ENOENT; >> + } >> + >> + digest_len = hash_digest_size[digest_cache->algo]; >> + >> + if (algo != digest_cache->algo) { >> + pr_debug("Algo mismatch for file %s, digest %s:%*phN in digest list %s (%s)\n", >> + pathname, hash_algo_name[algo], digest_len, digest, >> + digest_cache->path_str, >> + hash_algo_name[digest_cache->algo]); >> + return -ENOENT; >> + } >> + >> + key = digest_cache_hash_key(digest, digest_cache->num_slots); >> + >> + hlist_for_each_entry_rcu(entry, &digest_cache->slots[key], hnext) { >> + if (!memcmp(entry->digest, digest, digest_len)) { >> + pr_debug("Cache hit at depth %d for file %s, digest %s:%*phN in digest list %s\n", >> + search_depth, pathname, hash_algo_name[algo], >> + digest_len, digest, digest_cache->path_str); >> + return 0; >> + } >> + >> + search_depth++; >> + } >> + >> + pr_debug("Cache miss for file %s, digest %s:%*phN in digest list %s\n", >> + pathname, hash_algo_name[algo], digest_len, digest, >> + digest_cache->path_str); >> + return -ENOENT; >> +} >> diff --git a/security/integrity/digest_cache.h b/security/integrity/digest_cache.h >> index ff88e8593c6..01cd70f9850 100644 >> --- a/security/integrity/digest_cache.h >> +++ b/security/integrity/digest_cache.h >> @@ -66,6 +66,11 @@ static inline unsigned int digest_cache_hash_key(u8 *digest, >> void digest_cache_free(struct digest_cache *digest_cache); >> struct digest_cache *digest_cache_get(struct dentry *dentry, >> struct integrity_iint_cache *iint); >> +int digest_cache_init_htable(struct digest_cache *digest_cache, >> + u64 num_digests); >> +int digest_cache_add(struct digest_cache *digest_cache, u8 *digest); >> +int digest_cache_lookup(struct digest_cache *digest_cache, u8 *digest, >> + enum hash_algo algo, const char *pathname); >> #else >> static inline void digest_cache_free(struct digest_cache *digest_cache) >> { >> @@ -77,5 +82,24 @@ digest_cache_get(struct dentry *dentry, struct integrity_iint_cache *iint) >> return NULL; >> } >> >> +static inline int digest_cache_init_htable(struct digest_cache *digest_cache, >> + u64 num_digests) >> +{ >> + return -EOPNOTSUPP; >> +} >> + >> +static inline int digest_cache_add(struct digest_cache *digest_cache, >> + u8 *digest) >> +{ >> + return -EOPNOTSUPP; >> +} >> + >> +static inline int digest_cache_lookup(struct digest_cache *digest_cache, >> + u8 *digest, enum hash_algo algo, >> + const char *pathname) >> +{ >> + return -ENOENT; >> +} >> + >> #endif /* CONFIG_INTEGRITY_DIGEST_CACHE */ >> #endif /* _DIGEST_CACHE_H */ >> -- >> 2.34.1 > > Why all this complexity instead of using xarray? > > https://docs.kernel.org/core-api/xarray.html
Uhm, did I get correctly from the documentation that it isn't the optimal solution for hash tables?
Thanks
Roberto
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