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From: Daniel Colascione <dancol@google.com>
To: dancol@google.com, timmurray@google.com, nosh@google.com,
	nnk@google.com, lokeshgidra@google.com,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	selinux@vger.kernel.org
Subject: [PATCH v2 2/6] Add a concept of a "secure" anonymous file
Date: Tue, 11 Feb 2020 14:55:43 -0800
Message-ID: <20200211225547.235083-3-dancol@google.com> (raw)
In-Reply-To: <20200211225547.235083-1-dancol@google.com>

A secure anonymous file is one we hooked up to its own inode (as
opposed to the shared inode we use for non-secure anonymous files). A
new selinux hook gives security modules a chance to initialize, label,
and veto the creation of these secure anonymous files. Security
modules had limit ability to interact with non-secure anonymous files
due to all of these files sharing a single inode.

Signed-off-by: Daniel Colascione <dancol@google.com>
---
 fs/anon_inodes.c          | 45 ++++++++++++++++++++++++++++++---------
 include/linux/lsm_hooks.h |  8 +++++++
 include/linux/security.h  |  2 ++
 security/security.c       |  8 +++++++
 4 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index caa36019afca..d68d76523ad3 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -55,6 +55,23 @@ static struct file_system_type anon_inode_fs_type = {
 	.kill_sb	= kill_anon_super,
 };
 
+struct inode *anon_inode_make_secure_inode(const char *name,
+					   const struct file_operations *fops)
+{
+	struct inode *inode;
+	int error;
+	inode = alloc_anon_inode(anon_inode_mnt->mnt_sb);
+	if (IS_ERR(inode))
+		return ERR_PTR(PTR_ERR(inode));
+	inode->i_flags &= ~S_PRIVATE;
+	error =	security_inode_init_security_anon(inode, name, fops);
+	if (error) {
+		iput(inode);
+		return ERR_PTR(error);
+	}
+	return inode;
+}
+
 /**
  * anon_inode_getfile2 - creates a new file instance by hooking it up to
  *                       an anonymous inode, and a dentry that describe
@@ -72,7 +89,9 @@ static struct file_system_type anon_inode_fs_type = {
  * hence saving memory and avoiding code duplication for the file/inode/dentry
  * setup.  Returns the newly created file* or an error pointer.
  *
- * anon_inode_flags must be zero.
+ * If anon_inode_flags contains ANON_INODE_SECURE, create a new inode
+ * and enable security checks for it. Otherwise, attach a new file to
+ * a singleton placeholder inode with security checks disabled.
  */
 struct file *anon_inode_getfile2(const char *name,
 				 const struct file_operations *fops,
@@ -81,17 +100,23 @@ struct file *anon_inode_getfile2(const char *name,
 	struct inode *inode;
 	struct file *file;
 
-	if (anon_inode_flags)
+	if (anon_inode_flags & ~ANON_INODE_SECURE)
 		return ERR_PTR(-EINVAL);
 
-	inode =	anon_inode_inode;
-	if (IS_ERR(inode))
-		return ERR_PTR(-ENODEV);
-	/*
-	 * We know the anon_inode inode count is always
-	 * greater than zero, so ihold() is safe.
-	 */
-	ihold(inode);
+	if (anon_inode_flags & ANON_INODE_SECURE) {
+		inode =	anon_inode_make_secure_inode(name, fops);
+		if (IS_ERR(inode))
+			return ERR_PTR(PTR_ERR(inode));
+	} else {
+		inode =	anon_inode_inode;
+		if (IS_ERR(inode))
+			return ERR_PTR(-ENODEV);
+		/*
+		 * We know the anon_inode inode count is always
+		 * greater than zero, so ihold() is safe.
+		 */
+		ihold(inode);
+	}
 
 	if (fops->owner && !try_module_get(fops->owner)) {
 		file = ERR_PTR(-ENOENT);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 20d8cf194fb7..ba208ce5711d 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -215,6 +215,10 @@
  *	Returns 0 if @name and @value have been successfully set,
  *	-EOPNOTSUPP if no security attribute is needed, or
  *	-ENOMEM on memory allocation failure.
+ * @inode_init_security_anon:
+ *      Set up a secure anonymous inode.
+ *	Returns 0 on success. Returns -EPERM if	the security module denies
+ *	the creation of this inode.
  * @inode_create:
  *	Check permission to create a regular file.
  *	@dir contains inode structure of the parent of the new file.
@@ -1552,6 +1556,9 @@ union security_list_options {
 					const struct qstr *qstr,
 					const char **name, void **value,
 					size_t *len);
+	int (*inode_init_security_anon)(struct inode *inode,
+					const char *name,
+					const struct file_operations *fops);
 	int (*inode_create)(struct inode *dir, struct dentry *dentry,
 				umode_t mode);
 	int (*inode_link)(struct dentry *old_dentry, struct inode *dir,
@@ -1884,6 +1891,7 @@ struct security_hook_heads {
 	struct hlist_head inode_alloc_security;
 	struct hlist_head inode_free_security;
 	struct hlist_head inode_init_security;
+	struct hlist_head inode_init_security_anon;
 	struct hlist_head inode_create;
 	struct hlist_head inode_link;
 	struct hlist_head inode_unlink;
diff --git a/include/linux/security.h b/include/linux/security.h
index 64b19f050343..8625b647dd0b 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -320,6 +320,8 @@ void security_inode_free(struct inode *inode);
 int security_inode_init_security(struct inode *inode, struct inode *dir,
 				 const struct qstr *qstr,
 				 initxattrs initxattrs, void *fs_data);
+int security_inode_init_security_anon(struct inode *inode, const char *name,
+				      const struct file_operations *fops);
 int security_old_inode_init_security(struct inode *inode, struct inode *dir,
 				     const struct qstr *qstr, const char **name,
 				     void **value, size_t *len);
diff --git a/security/security.c b/security/security.c
index 565bc9b67276..78dc6096b30f 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1033,6 +1033,14 @@ int security_inode_init_security(struct inode *inode, struct inode *dir,
 }
 EXPORT_SYMBOL(security_inode_init_security);
 
+int
+security_inode_init_security_anon(struct inode *inode,
+				  const char *name,
+				  const struct file_operations *fops)
+{
+	return call_int_hook(inode_init_security_anon, 0, inode, name, fops);
+}
+
 int security_old_inode_init_security(struct inode *inode, struct inode *dir,
 				     const struct qstr *qstr, const char **name,
 				     void **value, size_t *len)
-- 
2.25.0.225.g125e21ebc7-goog


  parent reply index

Thread overview: 75+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 22:55 [PATCH v2 0/6] Harden userfaultfd Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 1/6] Add a new flags-accepting interface for anonymous inodes Daniel Colascione
2020-02-12 16:37   ` Stephen Smalley
2020-02-12 17:23     ` Daniel Colascione
2020-02-11 22:55 ` Daniel Colascione [this message]
2020-02-12 16:49   ` [PATCH v2 2/6] Add a concept of a "secure" anonymous file Stephen Smalley
2020-02-14 22:13   ` kbuild test robot
2020-02-11 22:55 ` [PATCH v2 3/6] Teach SELinux about a new userfaultfd class Daniel Colascione
2020-02-12 17:05   ` Stephen Smalley
2020-02-12 17:19     ` Daniel Colascione
2020-02-12 18:04       ` Stephen Smalley
2020-02-12 18:59         ` Stephen Smalley
2020-02-12 19:04           ` Daniel Colascione
2020-02-12 19:11             ` Stephen Smalley
2020-02-12 19:13               ` Daniel Colascione
2020-02-12 19:17               ` Stephen Smalley
2020-02-11 22:55 ` [PATCH v2 4/6] Wire UFFD up to SELinux Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 5/6] Let userfaultfd opt out of handling kernel-mode faults Daniel Colascione
2020-02-11 22:55 ` [PATCH v2 6/6] Add a new sysctl for limiting userfaultfd to user mode faults Daniel Colascione
2020-02-11 23:13 ` [PATCH v2 0/6] Harden userfaultfd Casey Schaufler
2020-02-11 23:27   ` Daniel Colascione
2020-02-12 16:09     ` Stephen Smalley
2020-02-21 17:56     ` James Morris
2020-02-12  7:50 ` Kees Cook
2020-02-12 16:54   ` Jann Horn
2020-02-12 17:14     ` Peter Xu
2020-02-12 19:41       ` Andrea Arcangeli
2020-02-12 20:04         ` Daniel Colascione
2020-02-12 23:41           ` Andrea Arcangeli
2020-02-12 17:12   ` Daniel Colascione
2020-02-14  3:26 ` [PATCH 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-02-14  3:26   ` [PATCH 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-02-14  3:26   ` [PATCH 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-02-14 16:39     ` Stephen Smalley
2020-02-14 17:21       ` Daniel Colascione
2020-02-14 18:02         ` Stephen Smalley
2020-02-14 18:08           ` Stephen Smalley
2020-02-14 20:24             ` Stephen Smalley
2020-02-14  3:26   ` [PATCH 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-25 23:02   ` [PATCH v2 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 13:53     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 13:58     ` Stephen Smalley
2020-03-26 17:59       ` Daniel Colascione
2020-03-26 17:37     ` Stephen Smalley
2020-03-25 23:02   ` [PATCH v2 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-25 23:49     ` Casey Schaufler
2020-03-26 18:14   ` [PATCH v3 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 18:14     ` [PATCH v3 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-26 19:00       ` Stephen Smalley
2020-03-26 18:14     ` [PATCH v3 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-26 19:02       ` Stephen Smalley
2020-03-26 18:14     ` [PATCH v3 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-03-26 20:06     ` [PATCH v4 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-03-26 20:06       ` [PATCH v4 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-03-27 13:40         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-03-27 13:41         ` Stephen Smalley
2020-03-26 20:06       ` [PATCH v4 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-01 21:39       ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 1/3] Add a new LSM-supporting anonymous inode interface Daniel Colascione
2020-05-07 16:02           ` James Morris
2020-04-01 21:39         ` [PATCH v5 2/3] Teach SELinux about anonymous inodes Daniel Colascione
2020-04-01 21:39         ` [PATCH v5 3/3] Wire UFFD up to SELinux Daniel Colascione
2020-04-13 13:29         ` [PATCH v5 0/3] SELinux support for anonymous inodes and UFFD Daniel Colascione
2020-04-22 16:55           ` James Morris
2020-04-22 17:12             ` Casey Schaufler
2020-04-23 22:24               ` Casey Schaufler
2020-04-27 16:18                 ` Casey Schaufler
2020-04-27 16:48                   ` Stephen Smalley
2020-04-27 17:12                     ` Casey Schaufler
2020-04-29 17:02                     ` Stephen Smalley
2020-04-27 17:15             ` Casey Schaufler
2020-04-27 19:40               ` Stephen Smalley

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