VFS: clean up and simplify getname_flags()

This removes a number of silly games around strncpy_from_user() in
do_getname(), and removes that helper function entirely.  We instead
make getname_flags() just use strncpy_from_user() properly directly.

Removing the wrapper function simplifies things noticeably, mostly
because we no longer play the unnecessary games with segments (x86
strncpy_from_user() no longer needs the hack), but also because the
empty path handling is just much more obvious.  The return value of
"strncpy_to_user()" is much more obvious than checking an odd error
return case from do_getname().

[ non-x86 architectures were notified of this change several weeks ago,
  since it is possible that they have copied the old broken x86
  strncpy_from_user. But nobody reacted, so .. See

    http://www.spinics.net/lists/linux-arch/msg17313.html

  for details ]

Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/namei.c b/fs/namei.c
index 0062dd17eb55d0f7bc365d0e06064cfb34d43449..494b1caa25f8f4f28339db0028e50cd72cb7925e 100644 (file)
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -116,47 +116,37 @@
  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
  * PATH_MAX includes the nul terminator --RR.
  */
-static int do_getname(const char __user *filename, char *page)
-{
-       int retval;
-       unsigned long len = PATH_MAX;
-
-       if (!segment_eq(get_fs(), KERNEL_DS)) {
-               if ((unsigned long) filename >= TASK_SIZE)
-                       return -EFAULT;
-               if (TASK_SIZE - (unsigned long) filename < PATH_MAX)
-                       len = TASK_SIZE - (unsigned long) filename;
-       }
-
-       retval = strncpy_from_user(page, filename, len);
-       if (retval > 0) {
-               if (retval < len)
-                       return 0;
-               return -ENAMETOOLONG;
-       } else if (!retval)
-               retval = -ENOENT;
-       return retval;
-}
-
 static char *getname_flags(const char __user *filename, int flags, int *empty)
 {
-       char *result = __getname();
-       int retval;
+       char *result = __getname(), *err;
+       int len;
 
-       if (!result)
+       if (unlikely(!result))
                return ERR_PTR(-ENOMEM);
 
-       retval = do_getname(filename, result);
-       if (retval < 0) {
-               if (retval == -ENOENT && empty)
+       len = strncpy_from_user(result, filename, PATH_MAX);
+       err = ERR_PTR(len);
+       if (unlikely(len < 0))
+               goto error;
+
+       /* The empty path is special. */
+       if (unlikely(!len)) {
+               if (empty)
                        *empty = 1;
-               if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
-                       __putname(result);
-                       return ERR_PTR(retval);
-               }
+               err = ERR_PTR(-ENOENT);
+               if (!(flags & LOOKUP_EMPTY))
+                       goto error;
        }
-       audit_getname(result);
-       return result;
+
+       err = ERR_PTR(-ENAMETOOLONG);
+       if (likely(len < PATH_MAX)) {
+               audit_getname(result);
+               return result;
+       }
+
+error:
+       __putname(result);
+       return err;
 }
 
 char *getname(const char __user * filename)