evm: posix acls modify i_mode
The posix xattr acls are 'system' prefixed, which normally would not
affect security.evm. An interesting side affect of writing posix xattr
acls is their modifying of the i_mode, which is included in security.evm.
This patch updates security.evm when posix xattr acls are written.
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 7d42475..73c008d 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -177,7 +177,14 @@
/*
* evm_protect_xattr - protect the EVM extended attribute
*
- * Prevent security.evm from being modified or removed.
+ * Prevent security.evm from being modified or removed without the
+ * necessary permissions or when the existing value is invalid.
+ *
+ * The posix xattr acls are 'system' prefixed, which normally would not
+ * affect security.evm. An interesting side affect of writing posix xattr
+ * acls is their modifying of the i_mode, which is included in security.evm.
+ * For posix xattr acls only, permit security.evm, even if it currently
+ * doesn't exist, to be updated.
*/
static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
@@ -187,9 +194,15 @@
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- } else if (!evm_protected_xattr(xattr_name))
- return 0;
-
+ } else if (!evm_protected_xattr(xattr_name)) {
+ if (!posix_xattr_acl(xattr_name))
+ return 0;
+ evm_status = evm_verify_current_integrity(dentry);
+ if ((evm_status == INTEGRITY_PASS) ||
+ (evm_status == INTEGRITY_NOLABEL))
+ return 0;
+ return -EPERM;
+ }
evm_status = evm_verify_current_integrity(dentry);
return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
}
@@ -240,7 +253,8 @@
void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
- if (!evm_initialized || !evm_protected_xattr(xattr_name))
+ if (!evm_initialized || (!evm_protected_xattr(xattr_name)
+ && !posix_xattr_acl(xattr_name)))
return;
evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);