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memcache: Properly track the size of talloc objects

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With memcache_add_talloc, the talloc object becomes part of the pool and
the memcache_element stores a pointer to the talloc object. The
size of the the talloc object was not used when tracking the used space,
allowing the cache to grow larger than defined in the memcache_init
call.

Fix this by adding the size of the talloc object to the used space.

Also record the initial size of the talloc object for proper adjustment
of the used space in the cache later. This is in case the size of the
talloc object is modified while being owned by the cache (e.g.
allocating talloc child objects). This should never happen, but better
be safe than ending up with a broken cache usage counter.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13865

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
This commit is contained in:
Christof Schmitt 2019-04-01 16:23:35 -07:00 committed by Jeremy Allison
parent 7c44f2f76e
commit a04ca6f343
1 changed files with 19 additions and 0 deletions
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19
lib/util/memcache.c
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@ -29,6 +29,7 @@ static struct memcache *global_cache;
struct memcache_talloc_value {
void *ptr;
size_t len;
};
struct memcache_element {
@ -213,6 +214,7 @@ static void memcache_delete_element(struct memcache *cache,
memcache_element_parse(e, &cache_key, &cache_value);
SMB_ASSERT(cache_value.length == sizeof(mtv));
memcpy(&mtv, cache_value.data, sizeof(mtv));
cache->size -= mtv.len;
TALLOC_FREE(mtv.ptr);
}
@ -283,6 +285,7 @@ void memcache_add(struct memcache *cache, enum memcache_number n,
SMB_ASSERT(cache_value.length == sizeof(mtv));
memcpy(&mtv, cache_value.data, sizeof(mtv));
cache->size -= mtv.len;
TALLOC_FREE(mtv.ptr);
}
/*
@ -290,6 +293,14 @@ void memcache_add(struct memcache *cache, enum memcache_number n,
*/
memcpy(cache_value.data, value.data, value.length);
e->valuelength = value.length;
if (memcache_is_talloc(e->n)) {
struct memcache_talloc_value mtv;
SMB_ASSERT(cache_value.length == sizeof(mtv));
memcpy(&mtv, cache_value.data, sizeof(mtv));
cache->size += mtv.len;
}
return;
}
@ -333,6 +344,13 @@ void memcache_add(struct memcache *cache, enum memcache_number n,
DLIST_ADD(cache->mru, e);
cache->size += element_size;
if (memcache_is_talloc(e->n)) {
struct memcache_talloc_value mtv;
SMB_ASSERT(cache_value.length == sizeof(mtv));
memcpy(&mtv, cache_value.data, sizeof(mtv));
cache->size += mtv.len;
}
memcache_trim(cache);
}
@ -349,6 +367,7 @@ void memcache_add_talloc(struct memcache *cache, enum memcache_number n,
return;
}
mtv.len = talloc_total_size(*ptr);
mtv.ptr = talloc_move(cache, ptr);
memcache_add(cache, n, key, data_blob_const(&mtv, sizeof(mtv)));
}