linux-kernel - [RFC PATCH] mm: create security context for memfd

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Date:   Tue, 25 Jan 2022 15:33:04 +0100
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        linux-security-module@...r.kernel.org,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH] mm: create security context for memfd_secret inodes

Create a security context for the inodes created by memfd_secret(2) via
the LSM hook inode_init_security_anon to allow a fine grained control.
As secret memory areas can affect hibernation and have a global shared
limit access control might be desirable.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
An alternative way of checking memfd_secret(2) is to create a new LSM
hook and e.g. for SELinux check via a new process class permission.
---
 mm/secretmem.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 22b310adb53d..b61cd2f661bc 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -164,11 +164,20 @@ static struct file *secretmem_file_create(unsigned long flags)
 {
 	struct file *file = ERR_PTR(-ENOMEM);
 	struct inode *inode;
+	const char *anon_name = "[secretmem]";
+	const struct qstr qname = QSTR_INIT(anon_name, strlen(anon_name));
+	int err;
 
 	inode = alloc_anon_inode(secretmem_mnt->mnt_sb);
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
+	err = security_inode_init_security_anon(inode, &qname, NULL);
+	if (err) {
+		file = ERR_PTR(err);
+		goto err_free_inode;
+	}
+
 	file = alloc_file_pseudo(inode, secretmem_mnt, "secretmem",
 				 O_RDWR, &secretmem_fops);
 	if (IS_ERR(file))
-- 
2.34.1