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landlock: Change landlock_restrict_self(2) check ordering 

According to the Landlock goal to be a security feature available to
unprivileges processes, it makes more sense to first check for
no_new_privs before checking anything else (i.e. syscall arguments).

Merge inval_fd_enforce and unpriv_enforce_without_no_new_privs tests
into the new restrict_self_checks_ordering.  This is similar to the
previous commit checking other syscalls.

Link: https://lore.kernel.org/r/20220506160820.524344-10-mic@digikod.net
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Mickaël Salaün 2022-05-06 18:08:19 +02:00
parent 589172e563
commit eba39ca4b1
No known key found for this signature in database
GPG Key ID: E5E3D0E88C82F6D2
2 changed files with 41 additions and 14 deletions
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8
security/landlock/syscalls.c
View File

@ -405,10 +405,6 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
if (!landlock_initialized)
return -EOPNOTSUPP;
/* No flag for now. */
if (flags)
return -EINVAL;
/*
* Similar checks as for seccomp(2), except that an -EPERM may be
* returned.
@ -417,6 +413,10 @@ SYSCALL_DEFINE2(landlock_restrict_self, const int, ruleset_fd, const __u32,
!ns_capable_noaudit(current_user_ns(), CAP_SYS_ADMIN))
return -EPERM;
/* No flag for now. */
if (flags)
return -EINVAL;
/* Gets and checks the ruleset. */
ruleset = get_ruleset_from_fd(ruleset_fd, FMODE_CAN_READ);
if (IS_ERR(ruleset))

47
tools/testing/selftests/landlock/base_test.c
View File

@ -168,22 +168,49 @@ TEST(add_rule_checks_ordering)
ASSERT_EQ(0, close(ruleset_fd));
}
TEST(inval_fd_enforce)
/* Tests ordering of syscall argument and permission checks. */
TEST(restrict_self_checks_ordering)
{
const struct landlock_ruleset_attr ruleset_attr = {
.handled_access_fs = LANDLOCK_ACCESS_FS_EXECUTE,
};
struct landlock_path_beneath_attr path_beneath_attr = {
.allowed_access = LANDLOCK_ACCESS_FS_EXECUTE,
.parent_fd = -1,
};
const int ruleset_fd =
landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
ASSERT_LE(0, ruleset_fd);
path_beneath_attr.parent_fd =
open("/tmp", O_PATH | O_NOFOLLOW | O_DIRECTORY | O_CLOEXEC);
ASSERT_LE(0, path_beneath_attr.parent_fd);
ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
&path_beneath_attr, 0));
ASSERT_EQ(0, close(path_beneath_attr.parent_fd));
/* Checks unprivileged enforcement without no_new_privs. */
drop_caps(_metadata);
ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, landlock_restrict_self(-1, 0));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(-1, landlock_restrict_self(ruleset_fd, 0));
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
/* Checks invalid flags. */
ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
ASSERT_EQ(EINVAL, errno);
/* Checks invalid ruleset FD. */
ASSERT_EQ(-1, landlock_restrict_self(-1, 0));
ASSERT_EQ(EBADF, errno);
}
TEST(unpriv_enforce_without_no_new_privs)
{
int err;
drop_caps(_metadata);
err = landlock_restrict_self(-1, 0);
ASSERT_EQ(EPERM, errno);
ASSERT_EQ(err, -1);
/* Checks valid call. */
ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
ASSERT_EQ(0, close(ruleset_fd));
}
TEST(ruleset_fd_io)