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landlock: Various documentation improvements

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* Fix some typos, incomplete or confusing phrases.
* Split paragraphs where appropriate.
* List the same error code multiple times,
  if it has multiple possible causes.
* Bring wording closer to the man page wording,
  which has undergone more thorough review
  (esp. for LANDLOCK_ACCESS_FS_WRITE_FILE).
* Small semantic clarifications
  * Call the ephemeral port range "ephemeral"
  * Clarify reasons for EFAULT in landlock_add_rule()
  * Clarify @rule_type doc for landlock_add_rule()

This is a collection of small fixes which I collected when preparing the
corresponding man pages [1].

Cc: Alejandro Colomar <alx@kernel.org>
Cc: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20240715155554.2791018-1-gnoack@google.com [1]
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240715160328.2792835-2-gnoack@google.com
[mic: Add label to link, fix formatting spotted by make htmldocs,
synchronize userspace-api documentation's date]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Günther Noack 2024-07-15 16:03:29 +00:00 committed by Mickaël Salaün
parent 33c97e7c03
commit f4b89d8ce5
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3 changed files with 24 additions and 22 deletions
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2
Documentation/userspace-api/landlock.rst
View File

@ -8,7 +8,7 @@ Landlock: unprivileged access control
=====================================
:Author: Mickaël Salaün
:Date: April 2024
:Date: July 2024
The goal of Landlock is to enable to restrict ambient rights (e.g. global
filesystem or network access) for a set of processes. Because Landlock

27
include/uapi/linux/landlock.h
View File

@ -104,20 +104,21 @@ struct landlock_path_beneath_attr {
*/
struct landlock_net_port_attr {
/**
* @allowed_access: Bitmask of allowed access network for a port
* @allowed_access: Bitmask of allowed network actions for a port
* (cf. `Network flags`_).
*/
__u64 allowed_access;
/**
* @port: Network port in host endianness.
*
* It should be noted that port 0 passed to :manpage:`bind(2)` will
* bind to an available port from a specific port range. This can be
* configured thanks to the ``/proc/sys/net/ipv4/ip_local_port_range``
* sysctl (also used for IPv6). A Landlock rule with port 0 and the
* ``LANDLOCK_ACCESS_NET_BIND_TCP`` right means that requesting to bind
* on port 0 is allowed and it will automatically translate to binding
* on the related port range.
* It should be noted that port 0 passed to :manpage:`bind(2)` will bind
* to an available port from the ephemeral port range. This can be
* configured with the ``/proc/sys/net/ipv4/ip_local_port_range`` sysctl
* (also used for IPv6).
*
* A Landlock rule with port 0 and the ``LANDLOCK_ACCESS_NET_BIND_TCP``
* right means that requesting to bind on port 0 is allowed and it will
* automatically translate to binding on the related port range.
*/
__u64 port;
};
@ -138,10 +139,10 @@ struct landlock_net_port_attr {
* The following access rights apply only to files:
*
* - %LANDLOCK_ACCESS_FS_EXECUTE: Execute a file.
* - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. Note that
* you might additionally need the %LANDLOCK_ACCESS_FS_TRUNCATE right in order
* to overwrite files with :manpage:`open(2)` using ``O_TRUNC`` or
* :manpage:`creat(2)`.
* - %LANDLOCK_ACCESS_FS_WRITE_FILE: Open a file with write access. When
* opening files for writing, you will often additionally need the
* %LANDLOCK_ACCESS_FS_TRUNCATE right. In many cases, these system calls
* truncate existing files when overwriting them (e.g., :manpage:`creat(2)`).
* - %LANDLOCK_ACCESS_FS_READ_FILE: Open a file with read access.
* - %LANDLOCK_ACCESS_FS_TRUNCATE: Truncate a file with :manpage:`truncate(2)`,
* :manpage:`ftruncate(2)`, :manpage:`creat(2)`, or :manpage:`open(2)` with
@ -263,7 +264,7 @@ struct landlock_net_port_attr {
* These flags enable to restrict a sandboxed process to a set of network
* actions. This is supported since the Landlock ABI version 4.
*
* TCP sockets with allowed actions:
* The following access rights apply to TCP port numbers:
*
* - %LANDLOCK_ACCESS_NET_BIND_TCP: Bind a TCP socket to a local port.
* - %LANDLOCK_ACCESS_NET_CONNECT_TCP: Connect an active TCP socket to

17
security/landlock/syscalls.c
View File

@ -378,8 +378,7 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
* with the new rule.
* @rule_type: Identify the structure type pointed to by @rule_attr:
* %LANDLOCK_RULE_PATH_BENEATH or %LANDLOCK_RULE_NET_PORT.
* @rule_attr: Pointer to a rule (only of type &struct
* landlock_path_beneath_attr for now).
* @rule_attr: Pointer to a rule (matching the @rule_type).
* @flags: Must be 0.
*
* This system call enables to define a new rule and add it to an existing
@ -390,18 +389,20 @@ static int add_rule_net_port(struct landlock_ruleset *ruleset,
* - %EOPNOTSUPP: Landlock is supported by the kernel but disabled at boot time;
* - %EAFNOSUPPORT: @rule_type is %LANDLOCK_RULE_NET_PORT but TCP/IP is not
* supported by the running kernel;
* - %EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
* - %EINVAL: @flags is not 0;
* - %EINVAL: The rule accesses are inconsistent (i.e.
* &landlock_path_beneath_attr.allowed_access or
* &landlock_net_port_attr.allowed_access is not a subset of the
* ruleset handled accesses), or &landlock_net_port_attr.port is
* greater than 65535;
* - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access);
* &landlock_net_port_attr.allowed_access is not a subset of the ruleset
* handled accesses)
* - %EINVAL: &landlock_net_port_attr.port is greater than 65535;
* - %ENOMSG: Empty accesses (e.g. &landlock_path_beneath_attr.allowed_access is
* 0);
* - %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.
* - %EFAULT: @rule_attr was not a valid address.
*/
SYSCALL_DEFINE4(landlock_add_rule, const int, ruleset_fd,
const enum landlock_rule_type, rule_type,