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>

diff --git a/include/linux/security.h b/include/linux/security.h
index 4686491852a70b0665633ee1bce5e44d344b3aa3..c2af46264ae0fcd519897f4fbcc84b4cf40cba6e 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -26,6 +26,7 @@
 #include <linux/capability.h>
 #include <linux/slab.h>
 #include <linux/err.h>
+#include <linux/string.h>
 
 struct linux_binprm;
 struct cred;
@@ -306,6 +307,15 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *     Parse a string of security data filling in the opts structure
  *     @options string containing all mount options known by the LSM
  *     @opts binary data structure usable by the LSM
+ * @dentry_init_security:
+ *     Compute a context for a dentry as the inode is not yet available
+ *     since NFSv4 has no label backed by an EA anyway.
+ *     @dentry dentry to use in calculating the context.
+ *     @mode mode used to determine resource type.
+ *     @name name of the last path component used to create file
+ *     @ctx pointer to place the pointer to the resulting context in.
+ *     @ctxlen point to place the length of the resulting context.
+ *
  *
  * Security hooks for inode operations.
  *
@@ -1443,6 +1453,10 @@ struct security_operations {
        int (*sb_clone_mnt_opts) (const struct super_block *oldsb,
                                   struct super_block *newsb);
        int (*sb_parse_opts_str) (char *options, struct security_mnt_opts *opts);
+       int (*dentry_init_security) (struct dentry *dentry, int mode,
+                                       struct qstr *name, void **ctx,
+                                       u32 *ctxlen);
+
 
 #ifdef CONFIG_SECURITY_PATH
        int (*path_unlink) (struct path *dir, struct dentry *dentry);
@@ -1729,6 +1743,9 @@ int security_sb_set_mnt_opts(struct super_block *sb, struct security_mnt_opts *o
 int security_sb_clone_mnt_opts(const struct super_block *oldsb,
                                struct super_block *newsb);
 int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts);
+int security_dentry_init_security(struct dentry *dentry, int mode,
+                                       struct qstr *name, void **ctx,
+                                       u32 *ctxlen);
 
 int security_inode_alloc(struct inode *inode);
 void security_inode_free(struct inode *inode);
@@ -2035,6 +2052,16 @@ static inline int security_inode_alloc(struct inode *inode)
 static inline void security_inode_free(struct inode *inode)
 { }
 
+static inline int security_dentry_init_security(struct dentry *dentry,
+                                                int mode,
+                                                struct qstr *name,
+                                                void **ctx,
+                                                u32 *ctxlen)
+{
+       return -EOPNOTSUPP;
+}
+
+
 static inline int security_inode_init_security(struct inode *inode,
                                                struct inode *dir,
                                                const struct qstr *qstr,

diff --git a/security/capability.c b/security/capability.c
index 1728d4e375db509c4e192e0e69fb1a0ee020bf49..58578b4bdad48870c8cb93c546c1df7b38989afa 100644 (file)
--- 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 a3dce87d1aeffccb92181631ef2687baec41d36c..0fe2b2ee9545ee9e13a91ae7e5c55813a7c05f7f 100644 (file)
--- 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 5c6f2cd2d095ee8b2a4e828123c00f7966639b6a..b1f7bd727bd947c0a7dabc806b691555c77f02a3 100644 (file)
--- 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,