xattr: define vfs_getxattr_alloc and vfs_xattr_cmp
vfs_getxattr_alloc() and vfs_xattr_cmp() are two new kernel xattr helper
functions. vfs_getxattr_alloc() first allocates memory for the requested
xattr and then retrieves it. vfs_xattr_cmp() compares a given value with
the contents of an extended attribute.
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com>
diff --git a/fs/xattr.c b/fs/xattr.c
index f060663..851808c 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -166,6 +166,64 @@
}
EXPORT_SYMBOL_GPL(xattr_getsecurity);
+/*
+ * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
+ *
+ * Allocate memory, if not already allocated, or re-allocate correct size,
+ * before retrieving the extended attribute.
+ *
+ * Returns the result of alloc, if failed, or the getxattr operation.
+ */
+ssize_t
+vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
+ size_t xattr_size, gfp_t flags)
+{
+ struct inode *inode = dentry->d_inode;
+ char *value = *xattr_value;
+ int error;
+
+ error = xattr_permission(inode, name, MAY_READ);
+ if (error)
+ return error;
+
+ if (!inode->i_op->getxattr)
+ return -EOPNOTSUPP;
+
+ error = inode->i_op->getxattr(dentry, name, NULL, 0);
+ if (error < 0)
+ return error;
+
+ if (!value || (error > xattr_size)) {
+ value = krealloc(*xattr_value, error + 1, flags);
+ if (!value)
+ return -ENOMEM;
+ memset(value, 0, error + 1);
+ }
+
+ error = inode->i_op->getxattr(dentry, name, value, error);
+ *xattr_value = value;
+ return error;
+}
+
+/* Compare an extended attribute value with the given value */
+int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
+ const char *value, size_t size, gfp_t flags)
+{
+ char *xattr_value = NULL;
+ int rc;
+
+ rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
+ if (rc < 0)
+ return rc;
+
+ if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
+ rc = -EINVAL;
+ else
+ rc = 0;
+ kfree(xattr_value);
+ return rc;
+}
+
ssize_t
vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
{