From: Stephen Smalley <sds@tycho.nsa.gov>

This patch modifies tmpfs to call the inode_init_security LSM hook to set
up the incore inode security state for new inodes before the inode becomes
accessible via the dcache.

As there is no underlying storage of security xattrs in this case, it is
not necessary for the hook to return the (name, value, len) triple to the
tmpfs code, so this patch also modifies the SELinux hook function to
correctly handle the case where the (name, value, len) pointers are NULL. 

The hook call is needed in tmpfs in order to support proper security
labeling of tmpfs inodes (e.g.  for udev with tmpfs /dev in Fedora).  With
this change in place, we should then be able to remove the
security_inode_post_create/mkdir/...  hooks safely.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 mm/shmem.c               |   20 +++++++++++++++++++-
 security/selinux/hooks.c |   24 ++++++++++++++----------
 2 files changed, 33 insertions(+), 11 deletions(-)

diff -puN mm/shmem.c~tmpfs-enable-atomic-inode-security mm/shmem.c
--- devel/mm/shmem.c~tmpfs-enable-atomic-inode-security	2005-07-30 00:43:56.000000000 -0700
+++ devel-akpm/mm/shmem.c	2005-07-30 00:43:56.000000000 -0700
@@ -1607,6 +1607,15 @@ shmem_mknod(struct inode *dir, struct de
 	int error = -ENOSPC;
 
 	if (inode) {
+		error = security_inode_init_security(inode, dir, NULL, NULL,
+						     NULL);
+		if (error) {
+			if (error != -EOPNOTSUPP) {
+				iput(inode);
+				return error;
+			}
+			error = 0;
+		}
 		if (dir->i_mode & S_ISGID) {
 			inode->i_gid = dir->i_gid;
 			if (S_ISDIR(mode))
@@ -1616,7 +1625,6 @@ shmem_mknod(struct inode *dir, struct de
 		dir->i_ctime = dir->i_mtime = CURRENT_TIME;
 		d_instantiate(dentry, inode);
 		dget(dentry); /* Extra count - pin the dentry in core */
-		error = 0;
 	}
 	return error;
 }
@@ -1746,6 +1754,16 @@ static int shmem_symlink(struct inode *d
 	if (!inode)
 		return -ENOSPC;
 
+	error = security_inode_init_security(inode, dir, NULL, NULL,
+					     NULL);
+	if (error) {
+		if (error != -EOPNOTSUPP) {
+			iput(inode);
+			return error;
+		}
+		error = 0;
+	}
+
 	info = SHMEM_I(inode);
 	inode->i_size = len-1;
 	if (len <= (char *)inode - (char *)info) {
diff -puN security/selinux/hooks.c~tmpfs-enable-atomic-inode-security security/selinux/hooks.c
--- devel/security/selinux/hooks.c~tmpfs-enable-atomic-inode-security	2005-07-30 00:43:56.000000000 -0700
+++ devel-akpm/security/selinux/hooks.c	2005-07-30 00:43:56.000000000 -0700
@@ -2034,7 +2034,7 @@ static int selinux_inode_init_security(s
 	struct inode_security_struct *isec;
 	u32 newsid;
 	int rc;
-	char *namep, *context;
+	char *namep = NULL, *context;
 
 	tsec = current->security;
 	dsec = dir->i_security;
@@ -2059,17 +2059,21 @@ static int selinux_inode_init_security(s
 
 	inode_security_set_sid(inode, newsid);
 
-	namep = kstrdup(XATTR_SELINUX_SUFFIX, GFP_KERNEL);
-	if (!namep)
-		return -ENOMEM;
-	*name = namep;
+	if (name) {
+		namep = kstrdup(XATTR_SELINUX_SUFFIX, GFP_KERNEL);
+		if (!namep)
+			return -ENOMEM;
+		*name = namep;
+	}
 
-	rc = security_sid_to_context(newsid, &context, len);
-	if (rc) {
-		kfree(namep);
-		return rc;
+	if (value && len) {
+		rc = security_sid_to_context(newsid, &context, len);
+		if (rc) {
+			kfree(namep);
+			return rc;
+		}
+		*value = context;
 	}
-	*value = context;
 
 	isec->security_attr_init = 1;
 
_