Hi,
在 2022/8/30 19:22, Mickaël Salaün 写道:
On 27/08/2022 13:12, Xiu Jianfeng wrote:
This helper will be used in the next commit which supports chmod and
chown access rights restriction.
Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
---
security/landlock/fs.c | 67 ++++++++++++++++++++++++++++++------------
1 file changed, 49 insertions(+), 18 deletions(-)
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index c57f581a9cd5..4ef614a4ea22 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -38,6 +38,44 @@
#include "ruleset.h"
#include "setup.h"
+enum walk_result {
+ WALK_CONTINUE,
+ WALK_TO_REAL_ROOT,
+ WALK_TO_DISCONN_ROOT,
Why did you created these results instead of the ones I proposed?
+};
+
+/*
+ * walk to the visible parent, caller should call path_get()/path_put()
+ * before/after this helpler.
+ *
+ * Returns:
+ * - WALK_TO_REAL_ROOT if walk to the real root;
+ * - WALK_TO_DISCONN_ROOT if walk to disconnected root;
+ * - WALK_CONTINUE otherwise.
+ */
+static enum walk_result walk_to_visible_parent(struct path *path)
+{
+ struct dentry *parent_dentry;
+jump_up:
+ if (path->dentry == path->mnt->mnt_root) {
+ if (follow_up(path)) {
+ /* Ignores hidden mount points. */
+ goto jump_up;
+ } else {
+ /* Stop at the real root. */
+ return WALK_TO_REAL_ROOT;
+ }
+ }
+ /* Stops at disconnected root directories. */
+ if (unlikely(IS_ROOT(path->dentry)))
+ return WALK_TO_DISCONN_ROOT;
+ parent_dentry = dget_parent(path->dentry);
+ dput(path->dentry);
+ path->dentry = parent_dentry;
+
+ return WALK_CONTINUE;
+}
+
/* Underlying object management */
static void release_inode(struct landlock_object *const object)
@@ -539,8 +577,8 @@ static int check_access_path_dual(
* restriction.
*/
while (true) {
- struct dentry *parent_dentry;
const struct landlock_rule *rule;
+ enum walk_result wr;
Please make the names understandable. In this case this variable may not
be needed anyway.
/*
* If at least all accesses allowed on the destination are
@@ -588,20 +626,12 @@ static int check_access_path_dual(
if (allowed_parent1 && allowed_parent2)
break;
-jump_up:
- if (walker_path.dentry == walker_path.mnt->mnt_root) {
- if (follow_up(&walker_path)) {
- /* Ignores hidden mount points. */
- goto jump_up;
- } else {
- /*
- * Stops at the real root. Denies access
- * because not all layers have granted access.
- */
- break;
- }
- }
- if (unlikely(IS_ROOT(walker_path.dentry))) {
+ wr = walk_to_visible_parent(&walker_path);
+ switch (wr) {
+ case WALK_TO_REAL_ROOT:
+ /* Stop at the real root. */
+ goto out;
+ case WALK_TO_DISCONN_ROOT:
/*
* Stops at disconnected root directories. Only allows
* access to internal filesystems (e.g. nsfs, which is
@@ -609,12 +639,13 @@ static int check_access_path_dual(
*/
allowed_parent1 = allowed_parent2 =
!!(walker_path.mnt->mnt_flags & MNT_INTERNAL);
Why not include this check in the helper? This is then not checked in
patch 3 with current_check_access_path_context_only(), which is a bug.
I get your point, after moving it to the helper, here should be:
while (true) {
...
switch(walk_to_visible_parent(&walker_path)) {
case WALK_CONTINUE:
break;
case WALK_ALLOWED:
allowed_parent1 = allowed_parent2 = true;
goto out;
case WR_DENIED:
default:
allowed_parent1 = allowed_parent2 = false;
goto out;
}
}
+ goto out;
+ case WALK_CONTINUE:
+ default:
break;
}
- parent_dentry = dget_parent(walker_path.dentry);
- dput(walker_path.dentry);
- walker_path.dentry = parent_dentry;
}
+out:
path_put(&walker_path);
if (allowed_parent1 && allowed_parent2)
.
