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Message-ID: <9456ccf3-e2b3-bb65-f24f-e6d2761120e5@digikod.net>
Date: Tue, 17 May 2022 10:04:09 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
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: Re: [PATCH v5 05/15] landlock: landlock_add_rule syscall refactoring
You can rename the subject to "landlock: Refactor landlock_add_rule()"
On 16/05/2022 17:20, Konstantin Meskhidze wrote:
> Landlock_add_rule syscall was refactored to support new
> rule types in future Landlock versions. Add_rule_path_beneath()
nit: add_rule_path_beneath(), not Add_rule_path_beneath()
> helper was added to support current filesystem rules. It is called
> by the switch case.
You can rephrase (all commit messages) in the present form:
Refactor the landlock_add_rule() syscall with add_rule_path_beneath()
to support new…
Refactor the landlock_add_rule() syscall to easily support for a new
rule type in a following commit. The new add_rule_path_beneath() helper
supports current filesystem rules.
>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
>
> Changes since v3:
> * Split commit.
> * Refactoring landlock_add_rule syscall.
>
> Changes since v4:
> * Refactoring add_rule_path_beneath() and landlock_add_rule() functions
> to optimize code usage.
> * Refactoring base_test.c seltest: adds LANDLOCK_RULE_PATH_BENEATH
> rule type in landlock_add_rule() call.
>
> ---
> security/landlock/syscalls.c | 105 ++++++++++---------
> tools/testing/selftests/landlock/base_test.c | 4 +-
> 2 files changed, 59 insertions(+), 50 deletions(-)
>
> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> index 1db799d1a50b..412ced6c512f 100644
> --- a/security/landlock/syscalls.c
> +++ b/security/landlock/syscalls.c
> @@ -274,67 +274,23 @@ static int get_path_from_fd(const s32 fd, struct path *const path)
> return err;
> }
>
> -/**
> - * sys_landlock_add_rule - Add a new rule to a ruleset
> - *
> - * @ruleset_fd: File descriptor tied to the ruleset that should be extended
> - * with the new rule.
> - * @rule_type: Identify the structure type pointed to by @rule_attr (only
> - * LANDLOCK_RULE_PATH_BENEATH for now).
> - * @rule_attr: Pointer to a rule (only of type &struct
> - * landlock_path_beneath_attr for now).
> - * @flags: Must be 0.
> - *
> - * This system call enables to define a new rule and add it to an existing
> - * ruleset.
> - *
> - * Possible returned errors are:
> - *
> - * - 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);
> - * - 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;
> - * - EPERM: @ruleset_fd has no write access to the underlying ruleset;
> - * - EFAULT: @rule_attr inconsistency.
> - */
> -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)
> +static int add_rule_path_beneath(const int ruleset_fd, const void *const rule_attr)
> {
> struct landlock_path_beneath_attr path_beneath_attr;
> struct path path;
> struct landlock_ruleset *ruleset;
> int res, err;
>
> - if (!landlock_initialized)
> - return -EOPNOTSUPP;
> -
> - /* No flag for now. */
> - if (flags)
> - return -EINVAL;
> -
> /* Gets and checks the ruleset. */
Like I already said, this needs to stay in landlock_add_rule(). I think
there is some inconsistencies with other patches that rechange this
part. Please review your patches and make clean patches that don't
partially revert the previous ones.
> ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_WRITE);
> if (IS_ERR(ruleset))
> return PTR_ERR(ruleset);
>
> - if (rule_type != LANDLOCK_RULE_PATH_BENEATH) {
> - 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;
> - }
> + sizeof(path_beneath_attr));
> + if (res)
> + return -EFAULT;
>
> /*
> * Informs about useless rule: empty allowed_access (i.e. deny rules)
> @@ -370,6 +326,59 @@ SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
> return err;
> }
>
> +/**
> + * sys_landlock_add_rule - Add a new rule to a ruleset
> + *
> + * @ruleset_fd: File descriptor tied to the ruleset that should be extended
> + * with the new rule.
> + * @rule_type: Identify the structure type pointed to by @rule_attr (only
> + * LANDLOCK_RULE_PATH_BENEATH for now).
> + * @rule_attr: Pointer to a rule (only of type &struct
> + * landlock_path_beneath_attr for now).
> + * @flags: Must be 0.
> + *
> + * This system call enables to define a new rule and add it to an existing
> + * ruleset.
> + *
> + * Possible returned errors are:
> + *
> + * - 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 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 (e.g. file open
> + * without O_PATH);
> + * - EPERM: @ruleset_fd has no write access to the underlying ruleset;
> + * - EFAULT: @rule_attr inconsistency.
> + */
> +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)
> +{
> + int err;
> +
> + if (!landlock_initialized)
> + return -EOPNOTSUPP;
> +
> + /* No flag for now. */
> + if (flags)
> + return -EINVAL;
> +
> + switch (rule_type) {
> + case LANDLOCK_RULE_PATH_BENEATH:
> + err = add_rule_path_beneath(ruleset_fd, rule_attr);
> + break;
> + default:
> + err = -EINVAL;
> + break;
> + }
> + return err;
> +}
> +
> /* Enforcement */
>
> /**
> diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
> index da9290817866..0c4c3a538d54 100644
> --- a/tools/testing/selftests/landlock/base_test.c
> +++ b/tools/testing/selftests/landlock/base_test.c
> @@ -156,11 +156,11 @@ TEST(add_rule_checks_ordering)
> ASSERT_LE(0, ruleset_fd);
>
> /* Checks invalid flags. */
> - ASSERT_EQ(-1, landlock_add_rule(-1, 0, NULL, 1));
> + ASSERT_EQ(-1, landlock_add_rule(-1, LANDLOCK_RULE_PATH_BENEATH, NULL, 1));
This must not be changed! I specifically added these tests to make sure
no one change the argument ordering checks…
> ASSERT_EQ(EINVAL, errno);
>
> /* Checks invalid ruleset FD. */
> - ASSERT_EQ(-1, landlock_add_rule(-1, 0, NULL, 0));
> + ASSERT_EQ(-1, landlock_add_rule(-1, LANDLOCK_RULE_PATH_BENEATH, NULL, 0));
> ASSERT_EQ(EBADF, errno);
>
> /* Checks invalid rule type. */
> --
> 2.25.1
>
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