[PATCH] tmpfs: Enable atomic inode security labeling

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>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 0d627a37da954ea68663797d4d45bffaf5fd89b5..1f7aeb210c7bf4de0c845f65d9c2b2b77cfe8ef0 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1608,6 +1608,15 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
        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))
@@ -1617,7 +1626,6 @@ shmem_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
                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;
 }
@@ -1747,6 +1755,16 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
        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 --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 63701fe0e1ad695fc5ad14ac5c77d88725febbd8..265f33d3af9b1dd7d7b5cd88637d7e5053d01e92 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2032,9 +2032,9 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
        struct inode_security_struct *dsec;
        struct superblock_security_struct *sbsec;
        struct inode_security_struct *isec;
-       u32 newsid;
+       u32 newsid, clen;
        int rc;
-       char *namep, *context;
+       char *namep = NULL, *context;
 
        tsec = current->security;
        dsec = dir->i_security;
@@ -2059,17 +2059,22 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir,
 
        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, &clen);
+               if (rc) {
+                       kfree(namep);
+                       return rc;
+               }
+               *value = context;
+               *len = clen;
        }
-       *value = context;
 
        isec->security_attr_init = 1;