[RFC PATCH 3/5] Shadow directories: chdir, fchdir

[Jaroslav Sykora]

sys_chdir and sys_fchdir changes.

Signed-off-by: Jaroslav Sykora <[EMAIL PROTECTED]>

 fs/open.c |   79 ++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 73 insertions(+), 6 deletions(-)

--- orig/fs/open.c      2007-10-07 19:00:19.000000000 +0200
+++ new/fs/open.c       2007-10-16 21:04:56.000000000 +0200
@@ -476,13 +476,51 @@ asmlinkage long sys_access(const char __
        return sys_faccessat(AT_FDCWD, filename, mode);
 }
 
+static inline int read_fs_flags(void)
+{
+       int res;
+       read_lock(&current->fs->lock);
+       res = current->fs->flags;
+       read_unlock(&current->fs->lock);
+       return res;
+}
+
+void set_fs_shdwpwd(struct fs_struct *fs,
+                       struct vfsmount *mnt, struct dentry *dentry)
+{
+       struct dentry *old_dentry;
+       struct vfsmount *old_mnt;
+
+       BUG_ON(dentry != NULL && mnt == NULL);
+       write_lock(&fs->lock);
+       /* set shadow pwd */
+       old_dentry = fs->shdwpwd;
+       old_mnt = fs->shdwpwdmnt;
+       fs->shdwpwd = dget(dentry);
+       if (dentry)
+               fs->shdwpwdmnt = mntget(mnt);
+       else
+               /* PTR_ERR flag */
+               fs->shdwpwdmnt = mnt;
+       write_unlock(&fs->lock);
+
+       if (old_dentry) {
+               mntput(old_mnt);
+               dput(old_dentry);
+       }
+}
+
 asmlinkage long sys_chdir(const char __user * filename)
 {
        struct nameidata nd;
-       int error;
+       char *tmp = getname(filename);
+       int error = PTR_ERR(tmp);;
+
+       if (IS_ERR(tmp))
+               goto out_badname;
 
-       error = __user_walk(filename,
-                           LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd);
+       error = path_lookup(tmp, LOOKUP_FOLLOW | LOOKUP_DIRECTORY
+                       | LOOKUP_CHDIR, &nd);
        if (error)
                goto out;
 
@@ -490,11 +528,23 @@ asmlinkage long sys_chdir(const char __u
        if (error)
                goto dput_and_out;
 
-       set_fs_pwd(current->fs, nd.mnt, nd.dentry);
+       if (!(read_fs_flags() & SHDW_ENABLED))
+               goto set_std;
 
+       if (!(nd.flags & LOOKUP_INSHDW))
+               set_fs_shdwpwd(current->fs, NULL, NULL);
+       else
+               /* shadow == std */
+               set_fs_shdwpwd(current->fs, nd.mnt, nd.dentry);
+
+set_std:
+       /* set std cwd */
+       set_fs_pwd(current->fs, nd.mnt, nd.dentry);
 dput_and_out:
        path_release(&nd);
 out:
+       putname(tmp);
+out_badname:
        return error;
 }
 
@@ -520,8 +570,25 @@ asmlinkage long sys_fchdir(unsigned int 
                goto out_putf;
 
        error = file_permission(file, MAY_EXEC);
-       if (!error)
-               set_fs_pwd(current->fs, mnt, dentry);
+       if (error)
+               goto out_putf;
+
+       set_fs_pwd(current->fs, mnt, dentry);
+
+       if (!(read_fs_flags() & SHDW_ENABLED))
+               /* shadow dirs aren't enabled */
+               goto out_putf;
+
+       if (get_file_shdwdir(file, &dentry, &mnt))
+               /* some error ocured */
+               set_fs_shdwpwd(current->fs, NULL, NULL);
+       else {
+               /* ok */
+               set_fs_shdwpwd(current->fs, mnt, dentry);
+               mntput(mnt);
+               dput(dentry);
+       }
+
 out_putf:
        fput(file);
 out:
-
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