9p: attach-per-user

The 9P2000 protocol requires the authentication and permission checks to be
done in the file server. For that reason every user that accesses the file
server tree has to authenticate and attach to the server separately.
Multiple users can share the same connection to the server.

Currently v9fs does a single attach and executes all I/O operations as a
single user. This makes using v9fs in multiuser environment unsafe as it
depends on the client doing the permission checking.

This patch improves the 9P2000 support by allowing every user to attach
separately. The patch defines three modes of access (new mount option
'access'):

- attach-per-user (access=user) (default mode for 9P2000.u)
 If a user tries to access a file served by v9fs for the first time, v9fs
 sends an attach command to the server (Tattach) specifying the user. If
 the attach succeeds, the user can access the v9fs tree.
 As there is no uname->uid (string->integer) mapping yet, this mode works
 only with the 9P2000.u dialect.

- allow only one user to access the tree (access=<uid>)
 Only the user with uid can access the v9fs tree. Other users that attempt
 to access it will get EPERM error.

- do all operations as a single user (access=any) (default for 9P2000)
 V9fs does a single attach and all operations are done as a single user.
 If this mode is selected, the v9fs behavior is identical with the current
 one.

Signed-off-by: Latchesar Ionkov <lucho@ionkov.net>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

1 files changed, 10 insertions, 10 deletions

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index f08a35d2973a..175b4d9bf3f8 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -364,7 +364,7 @@ static int v9fs_remove(struct inode *dir, struct dentry *file, int rmdir)
 	file_inode = file->d_inode;
 	v9ses = v9fs_inode2v9ses(file_inode);
 	v9fid = v9fs_fid_clone(file);
-	if(IS_ERR(v9fid))
+	if (IS_ERR(v9fid))
 		return PTR_ERR(v9fid);
 
 	return p9_client_remove(v9fid);
@@ -398,7 +398,7 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
 	fid = NULL;
 	name = (char *) dentry->d_name.name;
 	dfid = v9fs_fid_clone(dentry->d_parent);
-	if(IS_ERR(dfid)) {
+	if (IS_ERR(dfid)) {
 		err = PTR_ERR(dfid);
 		dfid = NULL;
 		goto error;
@@ -432,7 +432,7 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
 		goto error;
 	}
 
-	if(v9ses->cache)
+	if (v9ses->cache)
 		dentry->d_op = &v9fs_cached_dentry_operations;
 	else
 		dentry->d_op = &v9fs_dentry_operations;
@@ -593,7 +593,7 @@ static struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 	if (result < 0)
 		goto error;
 
-	if((fid->qid.version)&&(v9ses->cache))
+	if ((fid->qid.version) && (v9ses->cache))
 		dentry->d_op = &v9fs_cached_dentry_operations;
 	else
 		dentry->d_op = &v9fs_dentry_operations;
@@ -658,17 +658,17 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	old_inode = old_dentry->d_inode;
 	v9ses = v9fs_inode2v9ses(old_inode);
 	oldfid = v9fs_fid_lookup(old_dentry);
-	if(IS_ERR(oldfid))
+	if (IS_ERR(oldfid))
 		return PTR_ERR(oldfid);
 
 	olddirfid = v9fs_fid_clone(old_dentry->d_parent);
-	if(IS_ERR(olddirfid)) {
+	if (IS_ERR(olddirfid)) {
 		retval = PTR_ERR(olddirfid);
 		goto done;
 	}
 
 	newdirfid = v9fs_fid_clone(new_dentry->d_parent);
-	if(IS_ERR(newdirfid)) {
+	if (IS_ERR(newdirfid)) {
 		retval = PTR_ERR(newdirfid);
 		goto clunk_olddir;
 	}
@@ -682,7 +682,7 @@ v9fs_vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
 	}
 
 	v9fs_blank_wstat(&wstat);
-	wstat.muid = v9ses->name;
+	wstat.muid = v9ses->uname;
 	wstat.name = (char *) new_dentry->d_name.name;
 	retval = p9_client_wstat(oldfid, &wstat);
 
@@ -887,7 +887,7 @@ static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
 	retval = -EPERM;
 	v9ses = v9fs_inode2v9ses(dentry->d_inode);
 	fid = v9fs_fid_lookup(dentry);
-	if(IS_ERR(fid))
+	if (IS_ERR(fid))
 		return PTR_ERR(fid);
 
 	if (!v9fs_extended(v9ses))
@@ -1070,7 +1070,7 @@ v9fs_vfs_link(struct dentry *old_dentry, struct inode *dir,
 		old_dentry->d_name.name);
 
 	oldfid = v9fs_fid_clone(old_dentry);
-	if(IS_ERR(oldfid))
+	if (IS_ERR(oldfid))
 		return PTR_ERR(oldfid);
 
 	name = __getname();