Fix nasty ncpfs symlink handling bug.

This bug could cause oopses and page state corruption, because ncpfs
used the generic page-cache symlink handlign functions.  But those
functions only work if the page cache is guaranteed to be "stable", ie a
page that was installed when the symlink walk was started has to still
be installed in the page cache at the end of the walk.

We could have fixed ncpfs to not use the generic helper routines, but it
is in many ways much cleaner to instead improve on the symlink walking
helper routines so that they don't require that absolute stability.

We do this by allowing "follow_link()" to return a error-pointer as a
cookie, which is fed back to the cleanup "put_link()" routine.  This
also simplifies NFS symlink handling.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f9adf75fd9b4..67e6732d4fdc 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -993,8 +993,8 @@ struct inode_operations {
         int (*rename) (struct inode *, struct dentry *,
                         struct inode *, struct dentry *);
         int (*readlink) (struct dentry *, char __user *,int);
-        int (*follow_link) (struct dentry *, struct nameidata *);
-        void (*put_link) (struct dentry *, struct nameidata *);
+        void * (*follow_link) (struct dentry *, struct nameidata *);
+        void (*put_link) (struct dentry *, struct nameidata *, void *);
         void (*truncate) (struct inode *);
         int (*permission) (struct inode *, int, struct nameidata *);
         int (*setattr) (struct dentry *, struct iattr *);
@@ -1602,8 +1602,8 @@ extern struct file_operations generic_ro_fops;
 extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
 extern int vfs_follow_link(struct nameidata *, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
-extern int page_follow_link_light(struct dentry *, struct nameidata *);
-extern void page_put_link(struct dentry *, struct nameidata *);
+extern void *page_follow_link_light(struct dentry *, struct nameidata *);
+extern void page_put_link(struct dentry *, struct nameidata *, void *);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern struct inode_operations page_symlink_inode_operations;
 extern int generic_readlink(struct dentry *, char __user *, int);