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>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/open.c b/fs/open.c
index 1d9e5e98bf4e..044bfa891c94 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -757,6 +757,10 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
         f->f_op = fops_get(inode->i_fop);
         file_move(f, &inode->i_sb->s_files);
 
+        error = security_dentry_open(f);
+        if (error)
+                goto cleanup_all;
+
         if (!open && f->f_op)
                 open = f->f_op->open;
         if (open) {