From 944c74f472f926785b1948efa0e73e2f1b3b539b Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 16 Mar 2017 16:27:45 +0000 Subject: afs: Distinguish mountpoints from symlinks by file mode alone In AFS, mountpoints appear as symlinks with mode 0644 and normal symlinks have mode 0777, so use this to distinguish them rather than reading the content and parsing it. In the case of a mountpoint, the symlink body is a formatted string indicating the location of the target volume. Note that with this, kAFS no longer 'pre-fetches' the contents of symlinks, so afs_readpage() may fail with an access-denial because when the VFS calls d_automount(), it wraps the call in an credentials override that sets the initial creds - thereby preventing access to the caller's keyrings and the authentication keys held therein. To this end, a patch reverting that change to the VFS is required also. Reported-by: Jeffrey Altman Signed-off-by: David Howells --- fs/afs/inode.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) (limited to 'fs/afs/inode.c') diff --git a/fs/afs/inode.c b/fs/afs/inode.c index 299dbaeb2e2a..ade6ec3873cf 100644 --- a/fs/afs/inode.c +++ b/fs/afs/inode.c @@ -54,8 +54,21 @@ static int afs_inode_map_status(struct afs_vnode *vnode, struct key *key) inode->i_fop = &afs_dir_file_operations; break; case AFS_FTYPE_SYMLINK: - inode->i_mode = S_IFLNK | vnode->status.mode; - inode->i_op = &page_symlink_inode_operations; + /* Symlinks with a mode of 0644 are actually mountpoints. */ + if ((vnode->status.mode & 0777) == 0644) { + inode->i_flags |= S_AUTOMOUNT; + + spin_lock(&vnode->lock); + set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags); + spin_unlock(&vnode->lock); + + inode->i_mode = S_IFDIR | 0555; + inode->i_op = &afs_mntpt_inode_operations; + inode->i_fop = &afs_mntpt_file_operations; + } else { + inode->i_mode = S_IFLNK | vnode->status.mode; + inode->i_op = &page_symlink_inode_operations; + } inode_nohighmem(inode); break; default: @@ -79,18 +92,6 @@ static int afs_inode_map_status(struct afs_vnode *vnode, struct key *key) inode->i_generation = vnode->fid.unique; inode->i_version = vnode->status.data_version; inode->i_mapping->a_ops = &afs_fs_aops; - - /* check to see whether a symbolic link is really a mountpoint */ - if (vnode->status.type == AFS_FTYPE_SYMLINK) { - afs_mntpt_check_symlink(vnode, key); - - if (test_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags)) { - inode->i_mode = S_IFDIR | vnode->status.mode; - inode->i_op = &afs_mntpt_inode_operations; - inode->i_fop = &afs_mntpt_file_operations; - } - } - return 0; } -- cgit v1.2.3