diff options
| -rw-r--r-- | security/landlock/errata/abi-1.h | 16 | ||||
| -rw-r--r-- | security/landlock/fs.c | 40 |
2 files changed, 44 insertions, 12 deletions
diff --git a/security/landlock/errata/abi-1.h b/security/landlock/errata/abi-1.h new file mode 100644 index 000000000000..e8a2bff2e5b6 --- /dev/null +++ b/security/landlock/errata/abi-1.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/** + * DOC: erratum_3 + * + * Erratum 3: Disconnected directory handling + * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * + * This fix addresses an issue with disconnected directories that occur when a + * directory is moved outside the scope of a bind mount. The change ensures + * that evaluated access rights include both those from the disconnected file + * hierarchy down to its filesystem root and those from the related mount point + * hierarchy. This prevents access right widening through rename or link + * actions. + */ +LANDLOCK_ERRATUM(3) diff --git a/security/landlock/fs.c b/security/landlock/fs.c index 97cb7ba4eea4..2521acde6039 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -910,21 +910,31 @@ jump_up: break; } } + if (unlikely(IS_ROOT(walker_path.dentry))) { - /* - * Stops at disconnected root directories. Only allows - * access to internal filesystems (e.g. nsfs, which is - * reachable through /proc/<pid>/ns/<namespace>). - */ - if (walker_path.mnt->mnt_flags & MNT_INTERNAL) { + if (likely(walker_path.mnt->mnt_flags & MNT_INTERNAL)) { + /* + * Stops and allows access when reaching disconnected root + * directories that are part of internal filesystems (e.g. nsfs, + * which is reachable through /proc/<pid>/ns/<namespace>). + */ allowed_parent1 = true; allowed_parent2 = true; + break; } - break; + + /* + * We reached a disconnected root directory from a bind mount. + * Let's continue the walk with the mount point we missed. + */ + dput(walker_path.dentry); + walker_path.dentry = walker_path.mnt->mnt_root; + dget(walker_path.dentry); + } else { + parent_dentry = dget_parent(walker_path.dentry); + dput(walker_path.dentry); + walker_path.dentry = parent_dentry; } - parent_dentry = dget_parent(walker_path.dentry); - dput(walker_path.dentry); - walker_path.dentry = parent_dentry; } path_put(&walker_path); @@ -1022,6 +1032,9 @@ static access_mask_t maybe_remove(const struct dentry *const dentry) * file. While walking from @dir to @mnt_root, we record all the domain's * allowed accesses in @layer_masks_dom. * + * Because of disconnected directories, this walk may not reach @mnt_dir. In + * this case, the walk will continue to @mnt_dir after this call. + * * This is similar to is_access_to_paths_allowed() but much simpler because it * only handles walking on the same mount point and only checks one set of * accesses. @@ -1063,8 +1076,11 @@ static bool collect_domain_accesses( break; } - /* We should not reach a root other than @mnt_root. */ - if (dir == mnt_root || WARN_ON_ONCE(IS_ROOT(dir))) + /* + * Stops at the mount point or the filesystem root for a disconnected + * directory. + */ + if (dir == mnt_root || unlikely(IS_ROOT(dir))) break; parent_dentry = dget_parent(dir); |