SELinux: Improve read/write performance
It reduces the selinux overhead on read/write by only revalidating
permissions in selinux_file_permission if the task or inode labels have
changed or the policy has changed since the open-time check. A new LSM
hook, security_dentry_open, is added to capture the necessary state at open
time to allow this optimization.
(see http://marc.info/?l=selinux&m=118972995207740&w=2)
Signed-off-by: Yuichi Nakamura<ynakam@hitachisoft.jp>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index cf76150..97b7e27 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -14,6 +14,8 @@
* <dgoeddel@trustedcs.com>
* Copyright (C) 2006 Hewlett-Packard Development Company, L.P.
* Paul Moore, <paul.moore@hp.com>
+ * Copyright (C) 2007 Hitachi Software Engineering Co., Ltd.
+ * Yuichi Nakamura <ynakam@hitachisoft.jp>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2,
@@ -2464,7 +2466,7 @@
/* file security operations */
-static int selinux_file_permission(struct file *file, int mask)
+static int selinux_revalidate_file_permission(struct file *file, int mask)
{
int rc;
struct inode *inode = file->f_path.dentry->d_inode;
@@ -2486,6 +2488,25 @@
return selinux_netlbl_inode_permission(inode, mask);
}
+static int selinux_file_permission(struct file *file, int mask)
+{
+ struct inode *inode = file->f_path.dentry->d_inode;
+ struct task_security_struct *tsec = current->security;
+ struct file_security_struct *fsec = file->f_security;
+ struct inode_security_struct *isec = inode->i_security;
+
+ if (!mask) {
+ /* No permission to check. Existence test. */
+ return 0;
+ }
+
+ if (tsec->sid == fsec->sid && fsec->isid == isec->sid
+ && fsec->pseqno == avc_policy_seqno())
+ return selinux_netlbl_inode_permission(inode, mask);
+
+ return selinux_revalidate_file_permission(file, mask);
+}
+
static int selinux_file_alloc_security(struct file *file)
{
return file_alloc_security(file);
@@ -2725,6 +2746,34 @@
return file_has_perm(current, file, file_to_av(file));
}
+static int selinux_dentry_open(struct file *file)
+{
+ struct file_security_struct *fsec;
+ struct inode *inode;
+ struct inode_security_struct *isec;
+ inode = file->f_path.dentry->d_inode;
+ fsec = file->f_security;
+ isec = inode->i_security;
+ /*
+ * Save inode label and policy sequence number
+ * at open-time so that selinux_file_permission
+ * can determine whether revalidation is necessary.
+ * Task label is already saved in the file security
+ * struct as its SID.
+ */
+ fsec->isid = isec->sid;
+ fsec->pseqno = avc_policy_seqno();
+ /*
+ * Since the inode label or policy seqno may have changed
+ * between the selinux_inode_permission check and the saving
+ * of state above, recheck that access is still permitted.
+ * Otherwise, access might never be revalidated against the
+ * new inode label or new policy.
+ * This check is not redundant - do not remove.
+ */
+ return inode_has_perm(current, inode, file_to_av(file), NULL);
+}
+
/* task security operations */
static int selinux_task_create(unsigned long clone_flags)
@@ -4794,6 +4843,8 @@
.file_send_sigiotask = selinux_file_send_sigiotask,
.file_receive = selinux_file_receive,
+ .dentry_open = selinux_dentry_open,
+
.task_create = selinux_task_create,
.task_alloc_security = selinux_task_alloc_security,
.task_free_security = selinux_task_free_security,