staging: ramster: fix range checks in zcache_autocreate_pool()

If "pool_id" is negative then it leads to a read before the start of the
array.  If "cli_id" is out of bounds then it leads to a NULL dereference
of "cli".  GCC would have warned about that bug except that we
initialized the warning message away.

Also it's better to put the parameter names into the function
declaration in the .h file.  It serves as a kind of documentation.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ramster/zcache-main.c

@@ -1338,10 +1338,10 @@ static int zcache_local_new_pool(uint32_t flags)
 	return zcache_new_pool(LOCAL_CLIENT, flags);
 }
 
-int zcache_autocreate_pool(int cli_id, int pool_id, bool eph)
+int zcache_autocreate_pool(unsigned int cli_id, unsigned int pool_id, bool eph)
 {
 	struct tmem_pool *pool;
-	struct zcache_client *cli = NULL;
+	struct zcache_client *cli;
 	uint32_t flags = eph ? 0 : TMEM_POOL_PERSIST;
 	int ret = -1;
 
@@ -1350,8 +1350,10 @@ int zcache_autocreate_pool(int cli_id, int pool_id, bool eph)
 		goto out;
 	if (pool_id >= MAX_POOLS_PER_CLIENT)
 		goto out;
-	else if ((unsigned int)cli_id < MAX_CLIENTS)
-		cli = &zcache_clients[cli_id];
+	if (cli_id >= MAX_CLIENTS)
+		goto out;
+
+	cli = &zcache_clients[cli_id];
 	if ((eph && disable_cleancache) || (!eph && disable_frontswap)) {
 		pr_err("zcache_autocreate_pool: pool type disabled\n");
 		goto out;

drivers/staging/ramster/zcache.h

@@ -42,7 +42,7 @@ extern void zcache_decompress_to_page(char *, unsigned int, struct page *);
 #ifdef CONFIG_RAMSTER
 extern void *zcache_pampd_create(char *, unsigned int, bool, int,
 				struct tmem_handle *);
-extern int zcache_autocreate_pool(int, int, bool);
+int zcache_autocreate_pool(unsigned int cli_id, unsigned int pool_id, bool eph);
 #endif
 
 #define MAX_POOLS_PER_CLIENT 16