From ad4aff9ec25f400608283c10d634cc4eeda83a02 Mon Sep 17 00:00:00 2001
From: Casey Schaufler <casey@schaufler-ca.com>
Date: Tue, 12 Sep 2023 13:56:50 -0700
Subject: [PATCH] LSM: Create lsm_list_modules system call
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Create a system call to report the list of Linux Security Modules
that are active on the system. The list is provided as an array
of LSM ID numbers.
The calling application can use this list determine what LSM
specific actions it might take. That might include choosing an
output format, determining required privilege or bypassing
security module specific behavior.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Paul Moore <paul@paul-moore.com>
---
Documentation/userspace-api/lsm.rst | 3 +++
include/linux/syscalls.h | 1 +
kernel/sys_ni.c | 1 +
security/lsm_syscalls.c | 39 +++++++++++++++++++++++++++++
4 files changed, 44 insertions(+)
diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
index f8499f3e2826b..a76da373841b2 100644
--- a/Documentation/userspace-api/lsm.rst
+++ b/Documentation/userspace-api/lsm.rst
@@ -63,6 +63,9 @@ Get the specified security attributes of the current process
.. kernel-doc:: security/lsm_syscalls.c
:identifiers: sys_lsm_get_self_attr
+.. kernel-doc:: security/lsm_syscalls.c
+ :identifiers: sys_lsm_list_modules
+
Additional documentation
========================
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 4e1e56a24f1e7..feec5719750be 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -954,6 +954,7 @@ asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
size_t *size, __u32 flags);
asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
size_t size, __u32 flags);
+asmlinkage long sys_lsm_list_modules(u64 *ids, size_t *size, u32 flags);
/*
* Architecture-specific system calls
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 1f61b8452a6e7..9fa5989bf2cec 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -173,6 +173,7 @@ COND_SYSCALL(fadvise64_64);
COND_SYSCALL_COMPAT(fadvise64_64);
COND_SYSCALL(lsm_get_self_attr);
COND_SYSCALL(lsm_set_self_attr);
+COND_SYSCALL(lsm_list_modules);
/* CONFIG_MMU only */
COND_SYSCALL(swapon);
diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
index 226ae80d9683c..329aaca5efc03 100644
--- a/security/lsm_syscalls.c
+++ b/security/lsm_syscalls.c
@@ -55,3 +55,42 @@ SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
{
return security_getselfattr(attr, ctx, size, flags);
}
+
+/**
+ * sys_lsm_list_modules - Return a list of the active security modules
+ * @ids: the LSM module ids
+ * @size: pointer to size of @ids, updated on return
+ * @flags: reserved for future use, must be zero
+ *
+ * Returns a list of the active LSM ids. On success this function
+ * returns the number of @ids array elements. This value may be zero
+ * if there are no LSMs active. If @size is insufficient to contain
+ * the return data -E2BIG is returned and @size is set to the minimum
+ * required size. In all other cases a negative value indicating the
+ * error is returned.
+ */
+SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, size_t __user *, size,
+ u32, flags)
+{
+ size_t total_size = lsm_active_cnt * sizeof(*ids);
+ size_t usize;
+ int i;
+
+ if (flags)
+ return -EINVAL;
+
+ if (get_user(usize, size))
+ return -EFAULT;
+
+ if (put_user(total_size, size) != 0)
+ return -EFAULT;
+
+ if (usize < total_size)
+ return -E2BIG;
+
+ for (i = 0; i < lsm_active_cnt; i++)
+ if (put_user(lsm_idlist[i]->id, ids++))
+ return -EFAULT;
+
+ return lsm_active_cnt;
+}
--
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