[Pkg-clamav-commits] [SCM] Debian repository for ClamAV branch, debian/unstable, updated. debian/0.95+dfsg-1-6156-g094ec9b

[Török Edvin]

The following commit has been merged in the debian/unstable branch:
commit 75c7196180432613fc23edc4799ff08f0b8a32fa
Author: Török Edvin <edwin at clamav.net>
Date:   Wed Jan 6 19:53:07 2010 +0200

    Fix hash impl when replacing values.
    
    We never remove keys from the hash, we only replace keys that expire due to LRU,
    with the new keys. However the new key is not inserted in the same place as the
    old one! (it depends where it hashes) So we need to mark the old key as deleted,
    and not as empty. Otherwise future searches could miss keys that are in the
    hash!

diff --git a/libclamav/cache.c b/libclamav/cache.c
index 834fe4c..7fc29a3 100644
--- a/libclamav/cache.c
+++ b/libclamav/cache.c
@@ -182,6 +182,10 @@ int cache_check(unsigned char *hash, cli_ctx *ctx) {
     cli_md5_final(hash, &md5);
     return cache_lookup_hash(hash, ctx);
 }
+#if 0
+#define cli_calloc calloc
+#define cli_errmsg(x)
+#endif
 
 struct cache_key {
     char digest[16];
@@ -200,6 +204,8 @@ struct cache_set {
 };
 
 #define CACHE_INVALID_VERSION ~0u
+#define CACHE_KEY_DELETED ~0u
+#define CACHE_KEY_EMPTY 0
 
 /* size must be power of 2! */
 static int cacheset_init(struct cache_set* map, size_t maxsize, uint8_t loadfactor)
@@ -250,7 +256,17 @@ static void cacheset_lru_remove(struct cache_set *map, size_t howmany)
 	// Remove a key from the head of the list
 	old = map->lru_head;
 	map->lru_head = old->lru_next;
-	old->size = 0; /* this slot is now empty */
+	old->size = CACHE_KEY_DELETED;
+	/* This slot is now deleted, it is not empty,
+	 * because previously we could have inserted a key that has seen this
+	 * slot as occupied, to find that key we need to ensure that all keys
+	 * that were occupied when the key was inserted, are seen as occupied
+	 * when searching too.
+	 * Of course when inserting a new value, we treat deleted slots as
+	 * empty.
+	 * We only replace old values with new values, but there is no guarantee
+	 * that the newly inserted value would hash to same place as the value
+	 * we remove due to LRU! */
 	if (old == map->lru_tail)
 	    map->lru_tail = 0;
     }
@@ -282,18 +298,23 @@ static inline size_t hash(const unsigned char* k,const size_t len,const size_t S
 }
 
 int cacheset_lookup_internal(struct cache_set *map, const struct cache_key *key,
-			     uint32_t *insert_pos)
+			     uint32_t *insert_pos, int deletedok)
 {
     uint32_t idx = hash((const unsigned char*)key, sizeof(*key), map->capacity);
     uint32_t tries = 0;
     struct cache_key *k = &map->data[idx];
-    while (k->size) {
+    while (k->size != CACHE_KEY_EMPTY) {
 	if (k->size == key->size &&
 	    !memcmp(k->digest, key, 16)) {
 	    /* found key */
 	    *insert_pos = idx;
 	    return 1;
 	}
+       if (deletedok && k->size == CACHE_KEY_DELETED) {
+           /* treat deleted slot as empty */
+           *insert_pos = idx;
+           return 0;
+       }
 	idx = (idx + tries++)&(map->capacity-1);
 	k = &map->data[idx];
     }
@@ -332,7 +353,7 @@ static void cacheset_add(struct cache_set *map, const struct cache_key *key)
 	cacheset_lru_remove(map, 1);
     assert(map->elements < map->maxelements);
 
-    ret = cacheset_lookup_internal(map, key, &pos);
+    ret = cacheset_lookup_internal(map, key, &pos, 1);
     newkey = &map->data[pos];
     if (ret) {
 	/* was already added, remove from LRU list */
@@ -353,7 +374,7 @@ static int cacheset_lookup(struct cache_set *map, const struct cache_key *key)
     struct cache_key *newkey;
     int ret;
     uint32_t pos;
-    ret = cacheset_lookup_internal(map, key, &pos);
+    ret = cacheset_lookup_internal(map, key, &pos, 0);
     if (!ret)
 	return CACHE_INVALID_VERSION;
     newkey = &map->data[pos];

-- 
Debian repository for ClamAV