vfs: re-introduce MAY_CHDIR

Currently MAY_ACCESS means that filesystems must check the permissions
right then and not rely on cached results or the results of future
operations on the object.  This can be because of a call to sys_access() or
because of a call to chdir() which needs to check search without relying on
any future operations inside that dir.  I plan to use MAY_ACCESS for other
purposes in the security system, so I split the MAY_ACCESS and the
MAY_CHDIR cases.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by:  Stephen D. Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

4 files changed, 6 insertions, 5 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 3cdc5f78a406..431be0795b6b 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1016,7 +1016,7 @@ static int fuse_permission(struct inode *inode, int mask)
                    exist.  So if permissions are revoked this won't be
                    noticed immediately, only after the attribute
                    timeout has expired */
-        } else if (mask & MAY_ACCESS) {
+        } else if (mask & (MAY_ACCESS | MAY_CHDIR)) {
                 err = fuse_access(inode, mask);
         } else if ((mask & MAY_EXEC) && S_ISREG(inode->i_mode)) {
                 if (!(inode->i_mode & S_IXUGO)) {
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index e60416d3f818..832e9e239324 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1953,7 +1953,7 @@ int nfs_permission(struct inode *inode, int mask)
         if ((mask & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
                 goto out;
         /* Is this sys_access() ? */
-        if (mask & MAY_ACCESS)
+        if (mask & (MAY_ACCESS | MAY_CHDIR))
                 goto force_lookup;
 
         switch (inode->i_mode & S_IFMT) {
diff --git a/fs/open.c b/fs/open.c
index a54ed85209c1..0d1fa3dc0efb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -366,7 +366,7 @@ SYSCALL_DEFINE1(chdir, const char __user *, filename)
         if (error)
                 goto out;
 
-        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
+        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
         if (error)
                 goto dput_and_out;
 
@@ -395,7 +395,7 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd)
         if (!S_ISDIR(inode->i_mode))
                 goto out_putf;
 
-        error = inode_permission(inode, MAY_EXEC | MAY_ACCESS);
+        error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
         if (!error)
                 set_fs_pwd(current->fs, &file->f_path);
 out_putf:
@@ -413,7 +413,7 @@ SYSCALL_DEFINE1(chroot, const char __user *, filename)
         if (error)
                 goto out;
 
-        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_ACCESS);
+        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
         if (error)
                 goto dput_and_out;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 68ca1b0491af..7d94b72f0346 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -53,6 +53,7 @@ struct inodes_stat_t {
 #define MAY_APPEND 8
 #define MAY_ACCESS 16
 #define MAY_OPEN 32
+#define MAY_CHDIR 64
 
 /*
  * flags in file.f_mode.  Note that FMODE_READ and FMODE_WRITE must correspond