linux-kernel - [RFC PATCH 2/2] selinux: wire up new execstack LSM hook

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Date: Fri, 15 Mar 2024 19:08:47 +0100
From: Christian Göttsche <cgzones@...glemail.com>
To: linux-security-module@...r.kernel.org
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>,
	Jan Kara <jack@...e.cz>,
	Eric Biederman <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <jmorris@...ei.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Stephen Smalley <stephen.smalley.work@...il.com>,
	Ondrej Mosnacek <omosnace@...hat.com>,
	Khadija Kamran <kamrankhadijadj@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Roberto Sassu <roberto.sassu@...wei.com>,
	Guillaume Nault <gnault@...hat.com>,
	John Johansen <john.johansen@...onical.com>,
	Alfred Piccioni <alpic@...gle.com>,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	selinux@...r.kernel.org
Subject: [RFC PATCH 2/2] selinux: wire up new execstack LSM hook

Perform a process { execstack } check unless virtual memory is marked
executable by default.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
 security/selinux/hooks.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index a0fde0641f77..daf901916836 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -113,6 +113,8 @@ struct selinux_state selinux_state;
 /* SECMARK reference count */
 static atomic_t selinux_secmark_refcount = ATOMIC_INIT(0);
 
+static int default_noexec __ro_after_init;
+
 #ifdef CONFIG_SECURITY_SELINUX_DEVELOP
 static int selinux_enforcing_boot __initdata;
 
@@ -2221,6 +2223,18 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages)
 	return cap_sys_admin;
 }
 
+static int selinux_vm_execstack(void)
+{
+	u32 sid;
+
+	if (!default_noexec)
+		return 0;
+
+	sid = current_sid();
+	return avc_has_perm(sid, sid, SECCLASS_PROCESS,
+			    PROCESS__EXECSTACK, NULL);
+}
+
 /* binprm security operations */
 
 static u32 ptrace_parent_sid(void)
@@ -3767,8 +3781,6 @@ static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd,
 	return selinux_file_ioctl(file, cmd, arg);
 }
 
-static int default_noexec __ro_after_init;
-
 static int file_map_prot_check(struct file *file, unsigned long prot, int shared)
 {
 	const struct cred *cred = current_cred();
@@ -7120,6 +7132,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(quota_on, selinux_quota_on),
 	LSM_HOOK_INIT(syslog, selinux_syslog),
 	LSM_HOOK_INIT(vm_enough_memory, selinux_vm_enough_memory),
+	LSM_HOOK_INIT(vm_execstack, selinux_vm_execstack),
 
 	LSM_HOOK_INIT(netlink_send, selinux_netlink_send),
 
-- 
2.43.0