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>

3 files changed, 53 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index 1728d4e375db..58578b4bdad4 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -109,6 +109,13 @@ static int cap_sb_parse_opts_str(char *options, struct security_mnt_opts *opts)
 	return 0;
 }
 
+static int cap_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen)
+{
+	return 0;
+}
+
 static int cap_inode_alloc_security(struct inode *inode)
 {
 	return 0;
@@ -931,6 +938,7 @@ void __init security_fixup_ops(struct security_operations *ops)
 	set_to_cap_if_null(ops, sb_set_mnt_opts);
 	set_to_cap_if_null(ops, sb_clone_mnt_opts);
 	set_to_cap_if_null(ops, sb_parse_opts_str);
+	set_to_cap_if_null(ops, dentry_init_security);
 	set_to_cap_if_null(ops, inode_alloc_security);
 	set_to_cap_if_null(ops, inode_free_security);
 	set_to_cap_if_null(ops, inode_init_security);
diff --git a/security/security.c b/security/security.c
index a3dce87d1aef..0fe2b2ee9545 100644
--- a/security/security.c
+++ b/security/security.c
@@ -12,6 +12,7 @@
  */
 
 #include <linux/capability.h>
+#include <linux/dcache.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -324,6 +325,15 @@ void security_inode_free(struct inode *inode)
 	security_ops->inode_free_security(inode);
 }
 
+int security_dentry_init_security(struct dentry *dentry, int mode,
+					struct qstr *name, void **ctx,
+					u32 *ctxlen)
+{
+	return security_ops->dentry_init_security(dentry, mode, name,
+							ctx, ctxlen);
+}
+EXPORT_SYMBOL(security_dentry_init_security);
+
 int security_inode_init_security(struct inode *inode, struct inode *dir,
 				 const struct qstr *qstr,
 				 const initxattrs initxattrs, void *fs_data)
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,