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Message-ID: <20220621082313.3330667-7-konstantin.meskhidze@huawei.com>
Date: Tue, 21 Jun 2022 16:23:02 +0800
From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
To: <mic@...ikod.net>
CC: <willemdebruijn.kernel@...il.com>,
<linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>,
<netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>,
<anton.sirazetdinov@...wei.com>
Subject: [PATCH v6 06/17] landlock: refactors landlock_add_rule syscall
Modifies landlock_add_rule syscall to support
new rule types in future Landlock versions.
Adds add_rule_path_beneath() helper to support
current filesystem rules.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
---
Changes since v5:
* Refactors syscall landlock_add_rule() and
add_rule_path_beneath() helper to make argument
check ordering consistent and get rid of partial
revertings in following patches.
* Rolls back refactoring base_test.c seltest.
* Formats code with clang-format-14.
Changes since v4:
* Refactors add_rule_path_beneath() and landlock_add_rule() functions
to optimize code usage.
* Refactors base_test.c seltest: adds LANDLOCK_RULE_PATH_BENEATH
rule type in landlock_add_rule() call.
Changes since v3:
* Split commit.
* Refactors landlock_add_rule syscall.
---
security/landlock/syscalls.c | 99 +++++++++++++++++++-----------------
1 file changed, 52 insertions(+), 47 deletions(-)
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 5836736ce9d7..a209fd7d10c6 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -274,6 +274,47 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
return err;
}
+static int add_rule_path_beneath(struct landlock_ruleset *const ruleset,
+ const void *const rule_attr)
+{
+ struct landlock_path_beneath_attr path_beneath_attr;
+ struct path path;
+ int res, err;
+ u32 mask;
+
+ /* Copies raw user space buffer, only one type for now. */
+ res = copy_from_user(&path_beneath_attr, rule_attr,
+ sizeof(path_beneath_attr));
+ if (res)
+ return -EFAULT;
+
+ /*
+ * Informs about useless rule: empty allowed_access (i.e. deny rules)
+ * are ignored in path walks.
+ */
+ if (!path_beneath_attr.allowed_access)
+ return -ENOMSG;
+ /*
+ * Checks that allowed_access matches the @ruleset constraints
+ * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
+ */
+ mask = landlock_get_fs_access_mask(ruleset, 0);
+ if ((path_beneath_attr.allowed_access | mask) != mask)
+ return -EINVAL;
+
+ /* Gets and checks the new rule. */
+ err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
+ if (err)
+ return err;
+
+ /* Imports the new rule. */
+ err = landlock_append_fs_rule(ruleset, &path,
+ path_beneath_attr.allowed_access);
+ path_put(&path);
+
+ return err;
+}
+
/**
* sys_landlock_add_rule - Add a new rule to a ruleset
*
@@ -292,13 +333,14 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
*
* - EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
* - EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
- * &landlock_path_beneath_attr.allowed_access is not a subset of the
- * ruleset handled accesses);
+ * &landlock_path_beneath_attr.allowed_access is not a subset of the rule's
+ * accesses);
* - ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
* - EBADF: @ruleset_fd is not a file descriptor for the current thread, or a
* member of @rule_attr is not a file descriptor as expected;
* - EBADFD: @ruleset_fd is not a ruleset file descriptor, or a member of
- * @rule_attr is not the expected file descriptor type;
+ * @rule_attr is not the expected file descriptor type (e.g. file open
+ * without O_PATH);
* - EPERM: @ruleset_fd has no write access to the underlying ruleset;
* - EFAULT: @rule_attr inconsistency.
*/
@@ -306,10 +348,8 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
const enum landlock_rule_type, rule_type,
const void __user *const, rule_attr, const __u32, flags)
{
- struct landlock_path_beneath_attr path_beneath_attr;
- struct path path;
struct landlock_ruleset *ruleset;
- int res, err;
+ int err;
if (!landlock_initialized)
return -EOPNOTSUPP;
@@ -323,49 +363,14 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
if (IS_ERR(ruleset))
return PTR_ERR(ruleset);
- if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
+ switch (rule_type) {
+ case LANDLOCK_RULE_PATH_BENEATH:
+ err = add_rule_path_beneath(ruleset, rule_attr);
+ break;
+ default:
err = -EINVAL;
- goto out_put_ruleset;
- }
-
- /* Copies raw user space buffer, only one type for now. */
- res = copy_from_user(&path_beneath_attr, rule_attr,
- sizeof(path_beneath_attr));
- if (res) {
- err = -EFAULT;
- goto out_put_ruleset;
+ break;
}
-
- /*
- * Informs about useless rule: empty allowed_access (i.e. deny rules)
- * are ignored in path walks.
- */
- if (!path_beneath_attr.allowed_access) {
- err = -ENOMSG;
- goto out_put_ruleset;
- }
- /*
- * Checks that allowed_access matches the @ruleset constraints
- * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
- */
- if ((path_beneath_attr.allowed_access |
- landlock_get_fs_access_mask(ruleset, 0)) !=
- landlock_get_fs_access_mask(ruleset, 0)) {
- err = -EINVAL;
- goto out_put_ruleset;
- }
-
- /* Gets and checks the new rule. */
- err = get_path_from_fd(path_beneath_attr.parent_fd, &path);
- if (err)
- goto out_put_ruleset;
-
- /* Imports the new rule. */
- err = landlock_append_fs_rule(ruleset, &path,
- path_beneath_attr.allowed_access);
- path_put(&path);
-
-out_put_ruleset:
landlock_put_ruleset(ruleset);
return err;
}
--
2.25.1
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