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>

1 files changed, 24 insertions, 34 deletions

diff --git a/fs/namei.c b/fs/namei.c
index 0062dd17eb55..494b1caa25f8 100644
--- 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)