The patch below was submitted to be applied to the 5.18-stable tree.

I fail to see how this patch meets the stable kernel rules as found at Documentation/process/stable-kernel-rules.rst.

I could be totally wrong, and if so, please respond to stable@vger.kernel.org and let me know why this patch should be applied. Otherwise, it is now dropped from my patch queues, never to be seen again.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2cd7cd6eed88b8383cfddce589afe9c0ae1d19b4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= mic@digikod.net Date: Fri, 6 May 2022 18:10:53 +0200 Subject: [PATCH] landlock: Create find_rule() from unmask_layers() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

This refactoring will be useful in a following commit.

Reviewed-by: Paul Moore paul@paul-moore.com Link: https://lore.kernel.org/r/20220506161102.525323-4-mic@digikod.net Cc: stable@vger.kernel.org Signed-off-by: Mickaël Salaün mic@digikod.net

diff --git a/security/landlock/fs.c b/security/landlock/fs.c index f48c0a3b1e75..20953bff8fd5 100644 --- a/security/landlock/fs.c +++ b/security/landlock/fs.c @@ -183,23 +183,36 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,

/* Access-control management */

-static inline layer_mask_t -unmask_layers(const struct landlock_ruleset *const domain, - const struct path *const path, const access_mask_t access_request, - layer_mask_t layer_mask) +/* + * The lifetime of the returned rule is tied to @domain. + * + * Returns NULL if no rule is found or if @dentry is negative. + */ +static inline const struct landlock_rule * +find_rule(const struct landlock_ruleset *const domain, + const struct dentry *const dentry) { const struct landlock_rule *rule; const struct inode *inode; - size_t i;

- if (d_is_negative(path->dentry)) - /* Ignore nonexistent leafs. */ - return layer_mask; - inode = d_backing_inode(path->dentry); + /* Ignores nonexistent leafs. */ + if (d_is_negative(dentry)) + return NULL; + + inode = d_backing_inode(dentry); rcu_read_lock(); rule = landlock_find_rule( domain, rcu_dereference(landlock_inode(inode)->object)); rcu_read_unlock(); + return rule; +} + +static inline layer_mask_t unmask_layers(const struct landlock_rule *const rule, + const access_mask_t access_request, + layer_mask_t layer_mask) +{ + size_t layer_level; + if (!rule) return layer_mask;

@@ -210,8 +223,9 @@ unmask_layers(const struct landlock_ruleset *const domain, * the remaining layers for each inode, from the first added layer to * the last one. */ - for (i = 0; i < rule->num_layers; i++) { - const struct landlock_layer *const layer = &rule->layers[i]; + for (layer_level = 0; layer_level < rule->num_layers; layer_level++) { + const struct landlock_layer *const layer = + &rule->layers[layer_level]; const layer_mask_t layer_bit = BIT_ULL(layer->level - 1);

/* Checks that the layer grants access to the full request. */ @@ -269,8 +283,9 @@ static int check_access_path(const struct landlock_ruleset *const domain, while (true) { struct dentry *parent_dentry;

- layer_mask = unmask_layers(domain, &walker_path, access_request, - layer_mask); + layer_mask = + unmask_layers(find_rule(domain, walker_path.dentry), + access_request, layer_mask); if (layer_mask == 0) { /* Stops when a rule from each layer grants access. */ allowed = true;