linux-kernel - [PATCH] selinux: log anon inode class name

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Date:   Thu, 17 Feb 2022 15:34:55 +0100
From:   Christian Göttsche <cgzones@...glemail.com>
To:     selinux@...r.kernel.org
Cc:     James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Richard Guy Briggs <rgb@...hat.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: [PATCH] selinux: log anon inode class name

Log the anonymous inode class name in the security hook
inode_init_security_anon.  This name is the key for name based type
transitions on the anon_inode security class on creation.  Example:

    type=AVC msg=audit(02/16/22 22:02:50.585:216) : avc:  granted  { create } for  pid=2136 comm=mariadbd anonclass="[io_uring]" dev="anon_inodefs" ino=6871 scontext=system_u:system_r:mysqld_t:s0 tcontext=system_u:system_r:mysqld_iouring_t:s0 tclass=anon_inode

Add a new LSM audit data type holding the inode and the class name.

Also warn if the security hook gets called with no name set; currently
the only caller fs/anon_inodes.c:anon_inode_make_secure_inode() passes
one.

Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
---
 include/linux/lsm_audit.h |  5 +++++
 security/lsm_audit.c      | 21 +++++++++++++++++++++
 security/selinux/hooks.c  |  7 +++++--
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
index 17d02eda9538..8135a88d6d82 100644
--- a/include/linux/lsm_audit.h
+++ b/include/linux/lsm_audit.h
@@ -76,6 +76,7 @@ struct common_audit_data {
 #define LSM_AUDIT_DATA_IBENDPORT 14
 #define LSM_AUDIT_DATA_LOCKDOWN 15
 #define LSM_AUDIT_DATA_NOTIFICATION 16
+#define LSM_AUDIT_DATA_ANONINODE	17
 	union 	{
 		struct path path;
 		struct dentry *dentry;
@@ -96,6 +97,10 @@ struct common_audit_data {
 		struct lsm_ibpkey_audit *ibpkey;
 		struct lsm_ibendport_audit *ibendport;
 		int reason;
+		struct {
+			struct inode *inode;
+			const char *anonclass;
+		} anoninode_struct;
 	} u;
 	/* this union contains LSM specific data */
 	union {
diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 1897cbf6fc69..5545fed35539 100644
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -433,6 +433,27 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 		audit_log_format(ab, " lockdown_reason=\"%s\"",
 				 lockdown_reasons[a->u.reason]);
 		break;
+	case LSM_AUDIT_DATA_ANONINODE: {
+		struct dentry *dentry;
+		struct inode *inode;
+
+		rcu_read_lock();
+		inode = a->u.anoninode_struct.inode;
+		dentry = d_find_alias_rcu(inode);
+		if (dentry) {
+			audit_log_format(ab, " name=");
+			spin_lock(&dentry->d_lock);
+			audit_log_untrustedstring(ab, dentry->d_name.name);
+			spin_unlock(&dentry->d_lock);
+		}
+		audit_log_format(ab, " anonclass=");
+		audit_log_untrustedstring(ab, a->u.anoninode_struct.anonclass);
+		audit_log_format(ab, " dev=");
+		audit_log_untrustedstring(ab, inode->i_sb->s_id);
+		audit_log_format(ab, " ino=%lu", inode->i_ino);
+		rcu_read_unlock();
+		break;
+	}
 	} /* switch (a->type) */
 }
 
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index dafabb4dcc64..19c831d94d9b 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2932,6 +2932,8 @@ static int selinux_inode_init_security_anon(struct inode *inode,
 	if (unlikely(!selinux_initialized(&selinux_state)))
 		return 0;
 
+	WARN_ON(!name);
+
 	isec = selinux_inode(inode);
 
 	/*
@@ -2965,8 +2967,9 @@ static int selinux_inode_init_security_anon(struct inode *inode,
 	 * allowed to actually create this type of anonymous inode.
 	 */
 
-	ad.type = LSM_AUDIT_DATA_INODE;
-	ad.u.inode = inode;
+	ad.type = LSM_AUDIT_DATA_ANONINODE;
+	ad.u.anoninode_struct.inode = inode;
+	ad.u.anoninode_struct.anonclass = name ? (const char *)name->name : "unknown(null)";
 
 	return avc_has_perm(&selinux_state,
 			    tsec->sid,
-- 
2.35.1