linux-kernel - [PATCH v2 bpf-next 2/4] landlock: Use path_walk

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Message-ID: <20250603065920.3404510-3-song@kernel.org>
Date: Mon,  2 Jun 2025 23:59:18 -0700
From: Song Liu <song@...nel.org>
To: bpf@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org
Cc: kernel-team@...a.com,
	andrii@...nel.org,
	eddyz87@...il.com,
	ast@...nel.org,
	daniel@...earbox.net,
	martin.lau@...ux.dev,
	viro@...iv.linux.org.uk,
	brauner@...nel.org,
	jack@...e.cz,
	kpsingh@...nel.org,
	mattbobrowski@...gle.com,
	amir73il@...il.com,
	repnop@...gle.com,
	jlayton@...nel.org,
	josef@...icpanda.com,
	mic@...ikod.net,
	gnoack@...gle.com,
	m@...wtm.org,
	Song Liu <song@...nel.org>
Subject: [PATCH v2 bpf-next 2/4] landlock: Use path_walk_parent()

Use path_walk_parent() to walk a path up to its parent.

No functional changes intended.

Signed-off-by: Song Liu <song@...nel.org>
---
 security/landlock/fs.c | 31 ++++++++++---------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index 6fee7c20f64d..3adac544dc9e 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -837,8 +837,8 @@ static bool is_access_to_paths_allowed(
 	 * restriction.
 	 */
 	while (true) {
-		struct dentry *parent_dentry;
 		const struct landlock_rule *rule;
+		struct path root = {};
 
 		/*
 		 * If at least all accesses allowed on the destination are
@@ -895,34 +895,23 @@ static bool is_access_to_paths_allowed(
 		/* Stops when a rule from each layer grants access. */
 		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 (path_walk_parent(&walker_path, &root))
+			continue;
+
 		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>).
+			 * Stops at disconnected or real 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) {
 				allowed_parent1 = true;
 				allowed_parent2 = true;
 			}
-			break;
 		}
-		parent_dentry = dget_parent(walker_path.dentry);
-		dput(walker_path.dentry);
-		walker_path.dentry = parent_dentry;
+		break;
 	}
 	path_put(&walker_path);
 
-- 
2.47.1