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authorLinus Torvalds <torvalds@linux-foundation.org>2023-04-24 11:35:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2023-04-24 11:35:15 -0700
commit62443646a5fddd2c15dacd670fda84044ee7f748 (patch)
tree20d3dd05c13102013372c9d42b5c8bb5a1a97c32
parent5af4b523ba9be70372eafab02ebfb9babf77ec7d (diff)
parented35e2f2f0ded15df313ae6f8da21e85c8e1e493 (diff)
Merge tag 'landlock-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux
Pull landlock update from Mickaël Salaün: "Improve user space documentation" * tag 'landlock-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mic/linux: landlock: Clarify documentation for the LANDLOCK_ACCESS_FS_REFER right
-rw-r--r--include/uapi/linux/landlock.h46
1 files changed, 31 insertions, 15 deletions
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index f3223f964691..81d09ef9aa50 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -130,21 +130,37 @@ struct landlock_path_beneath_attr {
* - %LANDLOCK_ACCESS_FS_MAKE_BLOCK: Create (or rename or link) a block device.
* - %LANDLOCK_ACCESS_FS_MAKE_SYM: Create (or rename or link) a symbolic link.
* - %LANDLOCK_ACCESS_FS_REFER: Link or rename a file from or to a different
- * directory (i.e. reparent a file hierarchy). This access right is
- * available since the second version of the Landlock ABI. This is also the
- * only access right which is always considered handled by any ruleset in
- * such a way that reparenting a file hierarchy is always denied by default.
- * To avoid privilege escalation, it is not enough to add a rule with this
- * access right. When linking or renaming a file, the destination directory
- * hierarchy must also always have the same or a superset of restrictions of
- * the source hierarchy. If it is not the case, or if the domain doesn't
- * handle this access right, such actions are denied by default with errno
- * set to ``EXDEV``. Linking also requires a ``LANDLOCK_ACCESS_FS_MAKE_*``
- * access right on the destination directory, and renaming also requires a
- * ``LANDLOCK_ACCESS_FS_REMOVE_*`` access right on the source's (file or
- * directory) parent. Otherwise, such actions are denied with errno set to
- * ``EACCES``. The ``EACCES`` errno prevails over ``EXDEV`` to let user space
- * efficiently deal with an unrecoverable error.
+ * directory (i.e. reparent a file hierarchy).
+ *
+ * This access right is available since the second version of the Landlock
+ * ABI.
+ *
+ * This is the only access right which is denied by default by any ruleset,
+ * even if the right is not specified as handled at ruleset creation time.
+ * The only way to make a ruleset grant this right is to explicitly allow it
+ * for a specific directory by adding a matching rule to the ruleset.
+ *
+ * In particular, when using the first Landlock ABI version, Landlock will
+ * always deny attempts to reparent files between different directories.
+ *
+ * In addition to the source and destination directories having the
+ * %LANDLOCK_ACCESS_FS_REFER access right, the attempted link or rename
+ * operation must meet the following constraints:
+ *
+ * * The reparented file may not gain more access rights in the destination
+ * directory than it previously had in the source directory. If this is
+ * attempted, the operation results in an ``EXDEV`` error.
+ *
+ * * When linking or renaming, the ``LANDLOCK_ACCESS_FS_MAKE_*`` right for the
+ * respective file type must be granted for the destination directory.
+ * Otherwise, the operation results in an ``EACCES`` error.
+ *
+ * * When renaming, the ``LANDLOCK_ACCESS_FS_REMOVE_*`` right for the
+ * respective file type must be granted for the source directory. Otherwise,
+ * the operation results in an ``EACCES`` error.
+ *
+ * If multiple requirements are not met, the ``EACCES`` error code takes
+ * precedence over ``EXDEV``.
*
* .. warning::
*