:2.4.19: do_revalidate in chown

Greetings,
Requesting for comments on the below findings and the patch.

sys_stat() does a do_revalidate() after user_path_walk() but sys_chown() does not. This causes sys_chown() to use incorrect attribute information on distributed file systems. The sys_stat does do_revalidate() to revalidate the inodes for proper NFS attibute caching.
But when sys_chown calls chown_common after the user_path_walk, no checks are being done regarding the dentry values, which contain cached inode values. On Distributed File system environments there may be a likelyhood that these values may not be current and there is a likelihood of stale values being read.
Hence doing a do_revalidate before the chown calls will help address this issue.
Below is a patch which does that.

Regards,
Inguva

diff -urN ./fs/open.c ./fs-fixed/open.c
@@ -20,6 +20,8 @@
 
 #define special_file(m)

(S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

+extern int do_revalidate(struct dentry *);
+
int vfs_statfs(struct super_block *sb, struct statfs *buf) {
int retval = -ENODEV;
@@ -608,7 +610,9 @@

error = user_path_walk(filename, &nd);
if (!error) {

-  error = chown_common(nd.dentry, user, group);
+  error = do_revalidate(nd.dentry);
+  if (!error)

+ error = chown_common(nd.dentry, user, group);
path_release(&nd);
}
return error;
@@ -621,7 +625,9 @@

error = user_path_walk_link(filename, &nd);
if (!error) {

-  error = chown_common(nd.dentry, user, group);
+  error = do_revalidate(nd.dentry);
+  if (!error)

+ error = chown_common(nd.dentry, user, group);
path_release(&nd);
}
return error;
@@ -632,12 +638,15 @@
{
struct file * file;
int error = -EBADF;
-
- file = fget(fd);
- if (file) {
- error = chown_common(file->f_dentry, user, group);
- fput(file);
- }
+
+ if(!do_revalidate(file->f_dentry))

+  {
+  file = fget(fd);
+  if (file) {
+   error = chown_common(file->f_dentry, user, group);
+   fput(file);
+   }

+ }
return error;
}

diff -urN ./fs/stat.c ./fs-fixed/stat.c
@@ -13,11 +13,12 @@
 
 #include <asm/uaccess.h>
 
+extern int do_revalidate(struct dentry *);
+
 /*
  * Revalidate the inode. This is required for proper NFS attribute

caching.
*/
-static __inline__ int
-do_revalidate(struct dentry *dentry)
+int do_revalidate(struct dentry *dentry)
{
struct inode * inode = dentry->d_inode;
if (inode->i_op && inode->i_op->revalidate)