Re: [RFC PATCH v4 06/15] landlock: landlock_add_rule syscall refactoring

[Konstantin Meskhidze <konstantin.meskhidze@huawei.com>]

4/12/2022 2:12 PM, Mickaël Salaün пишет:
> 
> On 09/03/2022 14:44, Konstantin Meskhidze wrote:
>> Landlock_add_rule syscall was refactored to support new
>> rule types in future Landlock versions. Add_rule_path_beneath()
>> helper was added to support current filesystem rules. It is called
>> by the switch case.
>>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
>> ---
>>
>> Changes since v3:
>> * Split commit.
>> * Refactoring landlock_add_rule syscall.
>>
>> ---
>>   security/landlock/syscalls.c | 95 ++++++++++++++++++++----------------
>>   1 file changed, 53 insertions(+), 42 deletions(-)
>>
>> diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
>> index 5931b666321d..8c0f6165fe3a 100644
>> --- a/security/landlock/syscalls.c
>> +++ b/security/landlock/syscalls.c
>> @@ -274,54 +274,13 @@ 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 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)
>> +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;
>> -
>> -    if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
>> -        return -EINVAL;
>> -
>>       /* Copies raw user space buffer, only one type for now. */
>>       res = copy_from_user(&path_beneath_attr, rule_attr,
>>               sizeof(path_beneath_attr));
>> @@ -367,6 +326,58 @@ SYSCALL_DEFINE4(landlock_add_rule,
>>       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;
> 
> As you can see in my yesterday patch, the get_ruleset_from_fd() call 
> should be here.
> 
   Ok. Thnaks
> 
>> +
>> +    switch (rule_type) {
>> +    case LANDLOCK_RULE_PATH_BENEATH:
>> +        err = add_rule_path_beneath(ruleset_fd, rule_attr);
>> +        break;
>> +    default:
>> +        err = -EINVAL;
>> +    }
>> +    return err;
>> +}
>> +
>>   /* Enforcement */
>>
>>   /**
>> -- 
>> 2.25.1
>>
> .