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Message-ID: <20220829170401.834298-7-konstantin.meskhidze@huawei.com> Date: Tue, 30 Aug 2022 01:03:49 +0800 From: Konstantin Meskhidze <konstantin.meskhidze@...wei.com> To: <mic@...ikod.net> CC: <willemdebruijn.kernel@...il.com>, <gnoack3000@...il.com>, <linux-security-module@...r.kernel.org>, <netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>, <yusongping@...wei.com>, <hukeping@...wei.com>, <anton.sirazetdinov@...wei.com> Subject: [PATCH v7 06/18] landlock: refactor 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 v6: * None 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 6593381466e0..28acc4cef3e8 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 __user *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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