block/rnbd-clt: fix overlapping snprintf arguments

From: Arnd Bergmann <[email protected]>

The -Wrestrict warning (disabled by default) points out undefined behavior calling snprintf():

drivers/block/rnbd/rnbd-clt-sysfs.c: In function 'rnbd_clt_get_path_name':
drivers/block/rnbd/rnbd-clt-sysfs.c:486:8: error: 'snprintf' argument 4 overlaps destination object 'buf' [-Werror=restrict]

  486 |  ret = snprintf(buf, len, "%s@%s", buf, dev->sess->sessname);
      |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

drivers/block/rnbd/rnbd-clt-sysfs.c:472:67: note: destination object referenced by 'restrict'-qualified argument 1 was declared here
472 | static int rnbd_clt_get_path_name(struct rnbd_clt_dev *dev, char *buf,
| ~~~~~~^~~

This can be simplified by using a single snprintf() to print the whole buffer, avoiding the undefined behavior.

Fixes 91f4acb2801c ("block/rnbd-clt: support mapping two devices with the same name from different servers")

Signed-off-by Arnd Bergmann <[email protected]>

---
 drivers/block/rnbd/rnbd-clt-sysfs.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

drivers/block/rnbd/rnbd-clt-sysfs.c +1 -6

index d4aa6bfc9555..38251b749664 100644
@@ -479,11 +479,7 @@ static int rnbd_clt_get_path_name(struct rnbd_clt_dev *dev, char *buf,
        while ((s = strchr(pathname, '/')))
                s[0] = '!';
 
-       ret = snprintf(buf, len, "%s", pathname);
-       if (ret >= len)
-               return -ENAMETOOLONG;
-
-       ret = snprintf(buf, len, "%s@%s", buf, dev->sess->sessname);
+       ret = snprintf(buf, len, "%s@%s", pathname, dev->sess->sessname);
        if (ret >= len)
                return -ENAMETOOLONG;
 
--

2.29.2