Re: [PATCH] tmpfs: security xattr setting on inode creation

On Tue, Feb 28, 2012 at 7:46 AM, Andrew Morton [off-list ref]wrote:

On Fri, 24 Feb 2012 19:19:22 -0800 (PST)
Hugh Dickins [off-list ref] wrote:

quoted

+/*
+ * Callback for security_inode_init_security() for acquiring xattrs.
+ */
+static int shmem_initxattrs(struct inode *inode,
+                         const struct xattr *xattr_array,
+                         void *fs_info)
+{
+     struct shmem_inode_info *info = SHMEM_I(inode);
+     const struct xattr *xattr;
+     struct shmem_xattr *new_xattr;
+     size_t len;
+
+     for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+             new_xattr = shmem_xattr_alloc(xattr->value,

xattr->value_len);

quoted

+             if (!new_xattr)
+                     return -ENOMEM;
+
+             len = strlen(xattr->name) + 1;
+             new_xattr->name = kmalloc(XATTR_SECURITY_PREFIX_LEN + len,
+                                       GFP_KERNEL);
+             if (!new_xattr->name) {
+                     kfree(new_xattr);
+                     return -ENOMEM;
+             }
+
+             memcpy(new_xattr->name, XATTR_SECURITY_PREFIX,
+                    XATTR_SECURITY_PREFIX_LEN);
+             memcpy(new_xattr->name + XATTR_SECURITY_PREFIX_LEN,
+                    xattr->name, len);
+
+             spin_lock(&info->lock);
+             list_add(&new_xattr->list, &info->xattr_list);
+             spin_unlock(&info->lock);
+     }
+
+     return 0;
+}

So if there's a kmalloc failure partway through the array, we leave a
partially xattrified inode in place.

Are we sure this is OK?

I'm guessing Jarkko can clean that up a bit.  It wouldn't be a good idea to
leave inaccurate data structures laying around during failure cases.

Ryan