[PATCH -v2] SELinux/LSM: display SELinux mount options in /proc/mounts

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This patch causes SELinux mount options to show up in /proc/mounts.  As
with other code in the area seq_put errors are ignored.  Other LSM's
will not have their mount options displayed until they fill in their own
security_sb_show_options() function.

Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>

---

This patch is against a merged vfs-2.6:vfs-2.6.25 and selinux:for-akpm
repo.  It requires the a6307a583a073f85c38399c1e2c21dfe2d6a3da0
changeset in jame's repo to compile.  I'll let you and James decide if
we should push it through the VFS tree or the SELinux tree....

Only change from the last patch is the addition of " around mount
options which contain a comma example:
server:/export/ /import nfs rw,context="system_u:object_r:httpd_sys_content_t:s0:c1,c3",vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=X.X.X.X 0 0

 fs/namespace.c           |   12 +++++----
 include/linux/security.h |    9 +++++++
 security/dummy.c         |    6 +++++
 security/security.c      |    5 ++++
 security/selinux/hooks.c |   57 ++++++++++++++++++++++++++++++++++++++++++++-
 5 files changed, 82 insertions(+), 7 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 5df0ab2..496cfa3 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -748,7 +748,7 @@ struct proc_fs_info {
 	const char *str;
 };
 
-static void show_sb_opts(struct seq_file *m, struct super_block *sb)
+static int show_sb_opts(struct seq_file *m, struct super_block *sb)
 {
 	static const struct proc_fs_info fs_info[] = {
 		{ MS_SYNCHRONOUS, ",sync" },
@@ -762,6 +762,8 @@ static void show_sb_opts(struct seq_file *m, struct super_block *sb)
 		if (sb->s_flags & fs_infop->flag)
 			seq_puts(m, fs_infop->str);
 	}
+
+	return security_sb_show_options(m, sb);
 }
 
 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
@@ -804,9 +806,9 @@ static int show_vfsmnt(struct seq_file *m, void *v)
 	seq_putc(m, ' ');
 	show_type(m, mnt->mnt_sb);
 	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
-	show_sb_opts(m, mnt->mnt_sb);
+	err = show_sb_opts(m, mnt->mnt_sb);
 	show_mnt_opts(m, mnt);
-	if (mnt->mnt_sb->s_op->show_options)
+	if (!err && mnt->mnt_sb->s_op->show_options)
 		err = mnt->mnt_sb->s_op->show_options(m, mnt);
 	seq_puts(m, " 0 0\n");
 	return err;
@@ -863,8 +865,8 @@ static int show_mountinfo(struct seq_file *m, void *v)
 	seq_putc(m, ' ');
 	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
 	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
-	show_sb_opts(m, sb);
-	if (sb->s_op->show_options)
+	err = show_sb_opts(m, sb);
+	if (!err && sb->s_op->show_options)
 		err = sb->s_op->show_options(m, mnt);
 	seq_putc(m, '\n');
 	return err;
diff --git a/include/linux/security.h b/include/linux/security.h
index 0a10329..7a53dc1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -74,6 +74,7 @@ struct xfrm_selector;
 struct xfrm_policy;
 struct xfrm_state;
 struct xfrm_user_sec_ctx;
+struct seq_file;
 
 extern int cap_netlink_send(struct sock *sk, struct sk_buff *skb);
 extern int cap_netlink_recv(struct sk_buff *skb, int cap);
@@ -1259,6 +1260,7 @@ struct security_operations {
 	void (*sb_free_security) (struct super_block * sb);
 	int (*sb_copy_data)(char *orig, char *copy);
 	int (*sb_kern_mount) (struct super_block *sb, void *data);
+	int (*sb_show_options) (struct seq_file *m, struct super_block *sb);
 	int (*sb_statfs) (struct dentry *dentry);
 	int (*sb_mount) (char *dev_name, struct path *path,
 			 char *type, unsigned long flags, void *data);
@@ -1527,6 +1529,7 @@ int security_sb_alloc(struct super_block *sb);
 void security_sb_free(struct super_block *sb);
 int security_sb_copy_data(char *orig, char *copy);
 int security_sb_kern_mount(struct super_block *sb, void *data);
+int security_sb_show_options(struct seq_file *m, struct super_block *sb);
 int security_sb_statfs(struct dentry *dentry);
 int security_sb_mount(char *dev_name, struct path *path,
                        char *type, unsigned long flags, void *data);
@@ -1800,6 +1803,12 @@ static inline int security_sb_kern_mount (struct super_block *sb, void *data)
 	return 0;
 }
 
+static inline int security_sb_show_options(struct seq_file *m,
+					   struct super_block *sb)
+{
+	return 0;
+}
+
 static inline int security_sb_statfs (struct dentry *dentry)
 {
 	return 0;
diff --git a/security/dummy.c b/security/dummy.c
index 0be900e..a627adc 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -191,6 +191,11 @@ static int dummy_sb_kern_mount (struct super_block *sb, void *data)
 	return 0;
 }
 
+static int dummy_sb_show_options(struct seq_file *m, struct super_block *sb)
+{
+	return 0;
+}
+
 static int dummy_sb_statfs (struct dentry *dentry)
 {
 	return 0;
@@ -1017,6 +1022,7 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, sb_free_security);
 	set_to_dummy_if_null(ops, sb_copy_data);
 	set_to_dummy_if_null(ops, sb_kern_mount);
+	set_to_dummy_if_null(ops, sb_show_options);
 	set_to_dummy_if_null(ops, sb_statfs);
 	set_to_dummy_if_null(ops, sb_mount);
 	set_to_dummy_if_null(ops, sb_check_sb);
diff --git a/security/security.c b/security/security.c
index 805ed1d..7ca04df 100644
--- a/security/security.c
+++ b/security/security.c
@@ -255,6 +255,11 @@ int security_sb_kern_mount(struct super_block *sb, void *data)
 	return security_ops->sb_kern_mount(sb, data);
 }
 
+int security_sb_show_options(struct seq_file *m, struct super_block *sb)
+{
+	return security_ops->sb_show_options(m, sb);
+}
+
 int security_sb_statfs(struct dentry *dentry)
 {
 	return security_ops->sb_statfs(dentry);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index cec42ad..b8b9945 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -9,7 +9,8 @@
  *            James Morris <jmorris@xxxxxxxxxx>
  *
  *  Copyright (C) 2001,2002 Networks Associates Technology, Inc.
- *  Copyright (C) 2003 Red Hat, Inc., James Morris <jmorris@xxxxxxxxxx>
+ *  Copyright (C) 2003-2008 Red Hat, Inc., James Morris <jmorris@xxxxxxxxxx>
+ *					   Eric Paris <eparis@xxxxxxxxxx>
  *  Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
  *                          <dgoeddel@xxxxxxxxxxxxx>
  *  Copyright (C) 2006, 2007 Hewlett-Packard Development Company, L.P.
@@ -19,7 +20,7 @@
  *
  *	This program is free software; you can redistribute it and/or modify
  *	it under the terms of the GNU General Public License version 2,
- *      as published by the Free Software Foundation.
+ *	as published by the Free Software Foundation.
  */
 
 #include <linux/init.h>
@@ -944,6 +945,57 @@ out_err:
 	return rc;
 }
 
+void selinux_write_opts(struct seq_file *m, struct security_mnt_opts *opts)
+{
+	int i;
+	char *prefix;
+
+	for (i = 0; i < opts->num_mnt_opts; i++) {
+		char *has_comma = strchr(opts->mnt_opts[i], ',');
+
+		switch (opts->mnt_opts_flags[i]) {
+		case CONTEXT_MNT:
+			prefix = CONTEXT_STR;
+			break;
+		case FSCONTEXT_MNT:
+			prefix = FSCONTEXT_STR;
+			break;
+		case ROOTCONTEXT_MNT:
+			prefix = ROOTCONTEXT_STR;
+			break;
+		case DEFCONTEXT_MNT:
+			prefix = DEFCONTEXT_STR;
+			break;
+		default:
+			BUG();
+		};
+		/* we need a comma before each option */
+		seq_putc(m, ',');
+		seq_puts(m, prefix);
+		if (has_comma)
+			seq_putc(m, '\"');
+		seq_puts(m, opts->mnt_opts[i]);
+		if (has_comma)
+			seq_putc(m, '\"');
+	}
+}
+
+static int selinux_sb_show_options(struct seq_file *m, struct super_block *sb)
+{
+	struct security_mnt_opts opts;
+	int rc;
+
+	rc = selinux_get_mnt_opts(sb, &opts);
+	if (rc)
+		return rc;
+
+	selinux_write_opts(m, &opts);
+
+	security_free_mnt_opts(&opts);
+
+	return rc;
+}
+
 static inline u16 inode_mode_to_security_class(umode_t mode)
 {
 	switch (mode & S_IFMT) {
@@ -5310,6 +5362,7 @@ static struct security_operations selinux_ops = {
 	.sb_free_security =		selinux_sb_free_security,
 	.sb_copy_data =			selinux_sb_copy_data,
 	.sb_kern_mount =	        selinux_sb_kern_mount,
+	.sb_show_options =		selinux_sb_show_options,
 	.sb_statfs =			selinux_sb_statfs,
 	.sb_mount =			selinux_mount,
 	.sb_umount =			selinux_umount,


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