[PATCH] mm/zswap: change incorrect strncmp use to strcmp

[PATCH] mm/zswap: change incorrect strncmp use to strcmp

[Dan Streetman]

Change the use of strncmp in zswap_pool_find_get() to strcmp.

The use of strncmp is no longer correct, now that zswap_zpool_type is
not an array; sizeof() will return the size of a pointer, which isn't
the right length to compare.  We don't need to use strncmp anyway,
because the existing params and the passed in params are all guaranteed
to be null terminated, so strcmp should be used.

Reported-by: Weijie Yang <weijie.yang@samsung.com>
Cc: Seth Jennings <sjennings@variantweb.net>
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
---
 mm/zswap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 025f8dc..bf14508 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -541,6 +541,7 @@ static struct zswap_pool *zswap_pool_last_get(void)
 	return last;
 }
 
+/* type and compressor must be null-terminated */
 static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 {
 	struct zswap_pool *pool;
@@ -548,10 +549,9 @@ static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
 	assert_spin_locked(&zswap_pools_lock);
 
 	list_for_each_entry_rcu(pool, &zswap_pools, list) {
-		if (strncmp(pool->tfm_name, compressor, sizeof(pool->tfm_name)))
+		if (strcmp(pool->tfm_name, compressor))
 			continue;
-		if (strncmp(zpool_get_type(pool->zpool), type,
-			    sizeof(zswap_zpool_type)))
+		if (strcmp(zpool_get_type(pool->zpool), type))
 			continue;
 		/* if we can't get it, it's about to be destroyed */
 		if (!zswap_pool_get(pool))
-- 
2.5.0

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Re: [PATCH] mm/zswap: change incorrect strncmp use to strcmp

[Andrew Morton]

On Fri, 11 Dec 2015 18:33:11 -0500 Dan Streetman <ddstreet@ieee.org> wrote:

> Change the use of strncmp in zswap_pool_find_get() to strcmp.
> 
> The use of strncmp is no longer correct, now that zswap_zpool_type is
> not an array; sizeof() will return the size of a pointer, which isn't
> the right length to compare.

whoops

>  We don't need to use strncmp anyway,
> because the existing params and the passed in params are all guaranteed
> to be null terminated, so strcmp should be used.
> 

Thanks, I'll queue this for 4.4.

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