autofs4: use memchr() in invalid_string()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 4 insertions, 6 deletions

diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
index 463f798f71b3..84168c0dcc2d 100644
--- a/fs/autofs4/dev-ioctl.c
+++ b/fs/autofs4/dev-ioctl.c
@@ -54,11 +54,10 @@ static int check_name(const char *name)
  * Check a string doesn't overrun the chunk of
  * memory we copied from user land.
  */
-static int invalid_str(char *str, void *end)
+static int invalid_str(char *str, size_t size)
 {
-        while ((void *) str <= end)
-                if (!*str++)
-                        return 0;
+        if (memchr(str, 0, size))
+                return 0;
         return -EINVAL;
 }
 
@@ -138,8 +137,7 @@ static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
         }
 
         if (param->size > sizeof(*param)) {
-                err = invalid_str(param->path,
-                                 (void *) ((size_t) param + param->size));
+                err = invalid_str(param->path, param->size - sizeof(*param));
                 if (err) {
                         AUTOFS_WARN(
                           "path string terminator missing for cmd(0x%08x)",