diff options
Diffstat (limited to 'fs/namei.c')
| -rw-r--r-- | fs/namei.c | 72 |
1 files changed, 70 insertions, 2 deletions
@@ -960,6 +960,7 @@ static int follow_automount(struct path *path, unsigned flags, /* * Handle a dentry that is managed in some way. + * - Flagged for transit management (autofs) * - Flagged as mountpoint * - Flagged as automount point * @@ -979,6 +980,16 @@ static int follow_managed(struct path *path, unsigned flags) while (managed = ACCESS_ONCE(path->dentry->d_flags), managed &= DCACHE_MANAGED_DENTRY, unlikely(managed != 0)) { + /* Allow the filesystem to manage the transit without i_mutex + * being held. */ + if (managed & DCACHE_MANAGE_TRANSIT) { + BUG_ON(!path->dentry->d_op); + BUG_ON(!path->dentry->d_op->d_manage); + ret = path->dentry->d_op->d_manage(path->dentry, false); + if (ret < 0) + return ret == -EISDIR ? 0 : ret; + } + /* Transit to a mounted filesystem. */ if (managed & DCACHE_MOUNTED) { struct vfsmount *mounted = lookup_mnt(path); @@ -1012,7 +1023,7 @@ static int follow_managed(struct path *path, unsigned flags) return 0; } -int follow_down(struct path *path) +int follow_down_one(struct path *path) { struct vfsmount *mounted; @@ -1029,14 +1040,19 @@ int follow_down(struct path *path) /* * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we - * meet an automount point and we're not walking to "..". True is returned to + * meet a managed dentry and we're not walking to "..". True is returned to * continue, false to abort. */ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, struct inode **inode, bool reverse_transit) { + unsigned abort_mask = + reverse_transit ? 0 : DCACHE_MANAGE_TRANSIT; + while (d_mountpoint(path->dentry)) { struct vfsmount *mounted; + if (path->dentry->d_flags & abort_mask) + return true; mounted = __lookup_mnt(path->mnt, path->dentry, 1); if (!mounted) break; @@ -1087,6 +1103,57 @@ static int follow_dotdot_rcu(struct nameidata *nd) } /* + * Follow down to the covering mount currently visible to userspace. At each + * point, the filesystem owning that dentry may be queried as to whether the + * caller is permitted to proceed or not. + * + * Care must be taken as namespace_sem may be held (indicated by mounting_here + * being true). + */ +int follow_down(struct path *path, bool mounting_here) +{ + unsigned managed; + int ret; + + while (managed = ACCESS_ONCE(path->dentry->d_flags), + unlikely(managed & DCACHE_MANAGED_DENTRY)) { + /* Allow the filesystem to manage the transit without i_mutex + * being held. + * + * We indicate to the filesystem if someone is trying to mount + * something here. This gives autofs the chance to deny anyone + * other than its daemon the right to mount on its + * superstructure. + * + * The filesystem may sleep at this point. + */ + if (managed & DCACHE_MANAGE_TRANSIT) { + BUG_ON(!path->dentry->d_op); + BUG_ON(!path->dentry->d_op->d_manage); + ret = path->dentry->d_op->d_manage(path->dentry, mounting_here); + if (ret < 0) + return ret == -EISDIR ? 0 : ret; + } + + /* Transit to a mounted filesystem. */ + if (managed & DCACHE_MOUNTED) { + struct vfsmount *mounted = lookup_mnt(path); + if (!mounted) + break; + dput(path->dentry); + mntput(path->mnt); + path->mnt = mounted; + path->dentry = dget(mounted->mnt_root); + continue; + } + + /* Don't handle automount points here */ + break; + } + return 0; +} + +/* * Skip to top of mountpoint pile in refwalk mode for follow_dotdot() */ static void follow_mount(struct path *path) @@ -3530,6 +3597,7 @@ const struct inode_operations page_symlink_inode_operations = { }; EXPORT_SYMBOL(user_path_at); +EXPORT_SYMBOL(follow_down_one); EXPORT_SYMBOL(follow_down); EXPORT_SYMBOL(follow_up); EXPORT_SYMBOL(get_write_access); /* binfmt_aout */ |
