[PATCH v5 05/15] landlock: landlock_add_rule syscall refactoring

Konstantin Meskhidze konstantin.meskhidze at huawei.com
Thu May 19 09:23:53 UTC 2022



5/17/2022 11:04 AM, Mickaël Salaün пишет:
> 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()
> 
   Ok. Thanks. Will be renamed.

>> 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.
> 
   Ok. I will fix it.
> 
>>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.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.
> 
   Do you mean to leave this code as it its till adding network part
in commit landlock: TCP network hooks implementation?
  In this case this patch can be dropped.
> 
>>       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…

   I updated this code cause I got error in base_test.
   Ok. But in future commints I will order funtions calls in
   landlock_add_rule() so that base_test runs smoothly (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
>>
> .



More information about the Linux-security-module-archive mailing list