[PATCH 1/2] staging: zcache: fix length type mismatch

[PATCH 1/2] staging: zcache: fix length type mismatch

[Seth Jennings]

This fixes a type mismatch in the compression code where
a size_t pointer was cast to a unsigned int pointer.  On
little endian archs, there is no issue.  However on big
endian archs, the value is incorrect, taking the high
order bits and truncating the lower order bits.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
---
 drivers/staging/zcache/zcache-main.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
index 238d820..46c7c04 100644
--- a/drivers/staging/zcache/zcache-main.c
+++ b/drivers/staging/zcache/zcache-main.c
@@ -1170,14 +1170,14 @@ static atomic_t zcache_curr_pers_pampd_count = ATOMIC_INIT(0);
 static unsigned long zcache_curr_pers_pampd_count_max;
 
 /* forward reference */
-static int zcache_compress(struct page *from, void **out_va, size_t *out_len);
+static int zcache_compress(struct page *from, void **out_va, unsigned *out_len);
 
 static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
 				struct tmem_pool *pool, struct tmem_oid *oid,
 				 uint32_t index)
 {
 	void *pampd = NULL, *cdata;
-	size_t clen;
+	unsigned clen;
 	int ret;
 	unsigned long count;
 	struct page *page = (struct page *)(data);
@@ -1326,7 +1326,7 @@ static struct tmem_pamops zcache_pamops = {
 static DEFINE_PER_CPU(unsigned char *, zcache_dstmem);
 #define ZCACHE_DSTMEM_ORDER 1
 
-static int zcache_compress(struct page *from, void **out_va, size_t *out_len)
+static int zcache_compress(struct page *from, void **out_va, unsigned *out_len)
 {
 	int ret = 0;
 	unsigned char *dmem = __get_cpu_var(zcache_dstmem);
@@ -1339,7 +1339,7 @@ static int zcache_compress(struct page *from, void **out_va, size_t *out_len)
 	from_va = kmap_atomic(from, KM_USER0);
 	mb();
 	ret = zcache_comp_op(ZCACHE_COMPOP_COMPRESS, from_va, PAGE_SIZE, dmem,
-				(unsigned int *)out_len);
+				out_len);
 	BUG_ON(ret);
 	*out_va = dmem;
 	kunmap_atomic(from_va, KM_USER0);
-- 
1.7.5.4

Re: [PATCH 1/2] staging: zcache: fix length type mismatch

[Dan Carpenter]

[-- Attachment #1: Type: text/plain, Size: 578 bytes --]

On Tue, Feb 28, 2012 at 04:01:37PM -0600, Seth Jennings wrote:
> This fixes a type mismatch in the compression code where
> a size_t pointer was cast to a unsigned int pointer.  On
> little endian archs, there is no issue.  However on big
> endian archs, the value is incorrect, taking the high
> order bits and truncating the lower order bits.

I would think this would be a problem on any 64bit machine not just
big endian ones.  Since clen is half uninitialized we would likely
hit the clen > zbud_max_buddy_size() test.

Anyway the patch is right.

regards,
dan carpenter



[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 836 bytes --]