librdmacm: Fix an overflow bug in qsort comparison function

[ Upstream commit c4a5ac8 ]

The comparison function dev_cmp() doesn't work with 64b pointers in some
cases, as it casts the pointer to int. For example it's not able to sort
this list:
  {0xfffe0c2f0b00, 0xaaac741b4a90, 0xaaac741b4d70}

Fixes: e5d371c ("librdmacm: Globally store and sort IB device list")
Signed-off-by: Mark Zhang <[email protected]>
Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: Yishai Hadas <[email protected]>
Signed-off-by: Nicolas Morey <[email protected]>

librdmacm/cma.c

@@ -311,7 +311,7 @@ static void remove_cma_dev(struct cma_device *cma_dev)
 
 static int dev_cmp(const void *a, const void *b)
 {
-	return (int)(*(char *const *)a - *(char *const *)b);
+	return (*(uintptr_t *)a > *(uintptr_t *)b) - (*(uintptr_t *)a < *(uintptr_t *)b);
 }
 
 static int sync_devices_list(void)