Security: Add hook to calculate context based on a negative dentry.

There is a time where we need to calculate a context without the
inode having been created yet. To do this we take the negative dentry and
calculate a context based on the process and the parent directory contexts.

Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 5c6f2cd2d095..b1f7bd727bd9 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2515,6 +2515,40 @@ static void selinux_inode_free_security(struct inode *inode)
         inode_free_security(inode);
 }
 
+static int selinux_dentry_init_security(struct dentry *dentry, int mode,
+                                        struct qstr *name, void **ctx,
+                                        u32 *ctxlen)
+{
+        const struct cred *cred = current_cred();
+        struct task_security_struct *tsec;
+        struct inode_security_struct *dsec;
+        struct superblock_security_struct *sbsec;
+        struct inode *dir = dentry->d_parent->d_inode;
+        u32 newsid;
+        int rc;
+
+        tsec = cred->security;
+        dsec = dir->i_security;
+        sbsec = dir->i_sb->s_security;
+
+        if (tsec->create_sid && sbsec->behavior != SECURITY_FS_USE_MNTPOINT) {
+                newsid = tsec->create_sid;
+        } else {
+                rc = security_transition_sid(tsec->sid, dsec->sid,
+                                             inode_mode_to_security_class(mode),
+                                             name,
+                                             &newsid);
+                if (rc) {
+                        printk(KERN_WARNING
+                                "%s: security_transition_sid failed, rc=%d\n",
+                               __func__, -rc);
+                        return rc;
+                }
+        }
+
+        return security_sid_to_context(newsid, (char **)ctx, ctxlen);
+}
+
 static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
                                        const struct qstr *qstr, char **name,
                                        void **value, size_t *len)
@@ -5562,6 +5596,7 @@ static struct security_operations selinux_ops = {
         .sb_clone_mnt_opts =            selinux_sb_clone_mnt_opts,
         .sb_parse_opts_str =            selinux_parse_opts_str,
 
+        .dentry_init_security =         selinux_dentry_init_security,
 
         .inode_alloc_security =         selinux_inode_alloc_security,
         .inode_free_security =          selinux_inode_free_security,