4 files changed, 188 insertions, 4 deletions

diff --git a/security/integrity/evm/Kconfig b/security/integrity/evm/Kconfig
index e825e0ae78e7..d593346d0bba 100644
--- a/security/integrity/evm/Kconfig
+++ b/security/integrity/evm/Kconfig
@@ -42,6 +42,17 @@ config EVM_EXTRA_SMACK_XATTRS
 	  additional info to the calculation, requires existing EVM
 	  labeled file systems to be relabeled.
 
+config EVM_ADD_XATTRS
+	bool "Add additional EVM extended attributes at runtime"
+	depends on EVM
+	default n
+	help
+	  Allow userland to provide additional xattrs for HMAC calculation.
+
+	  When this option is enabled, root can add additional xattrs to the
+	  list used by EVM by writing them into
+	  /sys/kernel/security/integrity/evm/evm_xattrs.
+
 config EVM_LOAD_X509
 	bool "Load an X509 certificate onto the '.evm' trusted keyring"
 	depends on EVM && INTEGRITY_TRUSTED_KEYRING
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index caeea20670cc..494da5fcc092 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -208,7 +208,7 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 		return PTR_ERR(desc);
 
 	error = -ENODATA;
-	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+	list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
 		bool is_ima = false;
 
 		if (strcmp(xattr->name, XATTR_NAME_IMA) == 0)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 09582d4fc4a8..f9eff5041e4c 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -35,7 +35,7 @@ static const char * const integrity_status_msg[] = {
 };
 int evm_hmac_attrs;
 
-static struct xattr_list evm_config_default_xattrnames[] __ro_after_init = {
+static struct xattr_list evm_config_default_xattrnames[] = {
 #ifdef CONFIG_SECURITY_SELINUX
 	{.name = XATTR_NAME_SELINUX},
 #endif
@@ -101,7 +101,7 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
 	if (!(inode->i_opflags & IOP_XATTR))
 		return -EOPNOTSUPP;
 
-	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+	list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
 		error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
 		if (error < 0) {
 			if (error == -ENODATA)
@@ -228,7 +228,7 @@ static int evm_protected_xattr(const char *req_xattr_name)
 	struct xattr_list *xattr;
 
 	namelen = strlen(req_xattr_name);
-	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+	list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
 		if ((strlen(xattr->name) == namelen)
 		    && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
 			found = 1;
diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
index e44380f0cb45..a7a0a1acae99 100644
--- a/security/integrity/evm/evm_secfs.c
+++ b/security/integrity/evm/evm_secfs.c
@@ -15,14 +15,22 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <linux/audit.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include "evm.h"
 
 static struct dentry *evm_dir;
 static struct dentry *evm_init_tpm;
 static struct dentry *evm_symlink;
 
+#ifdef CONFIG_EVM_ADD_XATTRS
+static struct dentry *evm_xattrs;
+static DEFINE_MUTEX(xattr_list_mutex);
+static int evm_xattrs_locked;
+#endif
+
 /**
  * evm_read_key - read() for <securityfs>/evm
  *
@@ -109,6 +117,166 @@ static const struct file_operations evm_key_ops = {
 	.write		= evm_write_key,
 };
 
+#ifdef CONFIG_EVM_ADD_XATTRS
+/**
+ * evm_read_xattrs - read() for <securityfs>/evm_xattrs
+ *
+ * @filp: file pointer, not actually used
+ * @buf: where to put the result
+ * @count: maximum to send along
+ * @ppos: where to start
+ *
+ * Returns number of bytes read or error code, as appropriate
+ */
+static ssize_t evm_read_xattrs(struct file *filp, char __user *buf,
+			       size_t count, loff_t *ppos)
+{
+	char *temp;
+	int offset = 0;
+	ssize_t rc, size = 0;
+	struct xattr_list *xattr;
+
+	if (*ppos != 0)
+		return 0;
+
+	rc = mutex_lock_interruptible(&xattr_list_mutex);
+	if (rc)
+		return -ERESTARTSYS;
+
+	list_for_each_entry(xattr, &evm_config_xattrnames, list)
+		size += strlen(xattr->name) + 1;
+
+	temp = kmalloc(size + 1, GFP_KERNEL);
+	if (!temp)
+		return -ENOMEM;
+
+	list_for_each_entry(xattr, &evm_config_xattrnames, list) {
+		sprintf(temp + offset, "%s\n", xattr->name);
+		offset += strlen(xattr->name) + 1;
+	}
+
+	mutex_unlock(&xattr_list_mutex);
+	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
+
+	return rc;
+}
+
+/**
+ * evm_write_xattrs - write() for <securityfs>/evm_xattrs
+ * @file: file pointer, not actually used
+ * @buf: where to get the data from
+ * @count: bytes sent
+ * @ppos: where to start
+ *
+ * Returns number of bytes written or error code, as appropriate
+ */
+static ssize_t evm_write_xattrs(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	int len, err;
+	struct xattr_list *xattr, *tmp;
+	struct audit_buffer *ab;
+	struct iattr newattrs;
+	struct inode *inode;
+
+	if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked)
+		return -EPERM;
+
+	if (*ppos != 0)
+		return -EINVAL;
+
+	if (count > XATTR_NAME_MAX)
+		return -E2BIG;
+
+	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_EVM_XATTR);
+	if (IS_ERR(ab))
+		return PTR_ERR(ab);
+
+	xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL);
+	if (!xattr) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	xattr->name = memdup_user_nul(buf, count);
+	if (IS_ERR(xattr->name)) {
+		err = PTR_ERR(xattr->name);
+		xattr->name = NULL;
+		goto out;
+	}
+
+	/* Remove any trailing newline */
+	len = strlen(xattr->name);
+	if (xattr->name[len-1] == '\n')
+		xattr->name[len-1] = '\0';
+
+	if (strcmp(xattr->name, ".") == 0) {
+		evm_xattrs_locked = 1;
+		newattrs.ia_mode = S_IFREG | 0440;
+		newattrs.ia_valid = ATTR_MODE;
+		inode = evm_xattrs->d_inode;
+		inode_lock(inode);
+		err = simple_setattr(evm_xattrs, &newattrs);
+		inode_unlock(inode);
+		audit_log_format(ab, "locked");
+		if (!err)
+			err = count;
+		goto out;
+	}
+
+	audit_log_format(ab, "xattr=");
+	audit_log_untrustedstring(ab, xattr->name);
+
+	if (strncmp(xattr->name, XATTR_SECURITY_PREFIX,
+		    XATTR_SECURITY_PREFIX_LEN) != 0) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* Guard against races in evm_read_xattrs */
+	mutex_lock(&xattr_list_mutex);
+	list_for_each_entry(tmp, &evm_config_xattrnames, list) {
+		if (strcmp(xattr->name, tmp->name) == 0) {
+			err = -EEXIST;
+			mutex_unlock(&xattr_list_mutex);
+			goto out;
+		}
+	}
+	list_add_tail_rcu(&xattr->list, &evm_config_xattrnames);
+	mutex_unlock(&xattr_list_mutex);
+
+	audit_log_format(ab, " res=0");
+	audit_log_end(ab);
+	return count;
+out:
+	audit_log_format(ab, " res=%d", err);
+	audit_log_end(ab);
+	kfree(xattr->name);
+	kfree(xattr);
+	return err;
+}
+
+static const struct file_operations evm_xattr_ops = {
+	.read		= evm_read_xattrs,
+	.write		= evm_write_xattrs,
+};
+
+static int evm_init_xattrs(void)
+{
+	evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL,
+					    &evm_xattr_ops);
+	if (!evm_xattrs || IS_ERR(evm_xattrs))
+		return -EFAULT;
+
+	return 0;
+}
+#else
+static int evm_init_xattrs(void)
+{
+	return 0;
+}
+#endif
+
 int __init evm_init_secfs(void)
 {
 	int error = 0;
@@ -131,6 +299,11 @@ int __init evm_init_secfs(void)
 		goto out;
 	}
 
+	if (evm_init_xattrs() != 0) {
+		error = -EFAULT;
+		goto out;
+	}
+
 	return 0;
 out:
 	securityfs_remove(evm_symlink);