new helper: readlink_copy()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -4297,11 +4297,9 @@ SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newna
 	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
 }
 
-int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
+int readlink_copy(char __user *buffer, int buflen, const char *link)
 {
-	int len;
+	int len = PTR_ERR(link);
-
-	len = PTR_ERR(link);
 	if (IS_ERR(link))
 		goto out;
 
@@ -4313,7 +4311,7 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const c
 out:
 	return len;
 }
-EXPORT_SYMBOL(vfs_readlink);
+EXPORT_SYMBOL(readlink_copy);
 
 /*
  * A helper for ->readlink().  This should be used *ONLY* for symlinks that
@@ -4331,7 +4329,7 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 	if (IS_ERR(cookie))
 		return PTR_ERR(cookie);
 
-	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
+	res = readlink_copy(buffer, buflen, nd_get_link(&nd));
 	if (dentry->d_inode->i_op->put_link)
 		dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
 	return res;
@@ -4356,8 +4354,7 @@ static char *page_getlink(struct dentry * dentry, struct page **ppage)
 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
 	struct page *page = NULL;
-	char *s = page_getlink(dentry, &page);
+	int res = readlink_copy(buffer, buflen, page_getlink(dentry, &page));
-	int res = vfs_readlink(dentry,buffer,buflen,s);
 	if (page) {
 		kunmap(page);
 		page_cache_release(page);

fs/proc/namespaces.c

@@ -146,7 +146,7 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
 	struct task_struct *task;
 	void *ns;
 	char name[50];
-	int len = -EACCES;
+	int res = -EACCES;
 
 	task = get_proc_task(inode);
 	if (!task)
@@ -155,24 +155,18 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
 	if (!ptrace_may_access(task, PTRACE_MODE_READ))
 		goto out_put_task;
 
-	len = -ENOENT;
+	res = -ENOENT;
 	ns = ns_ops->get(task);
 	if (!ns)
 		goto out_put_task;
 
 	snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
-	len = strlen(name);
+	res = readlink_copy(buffer, buflen, name);
-
-	if (len > buflen)
-		len = buflen;
-	if (copy_to_user(buffer, name, len))
-		len = -EFAULT;
-
 	ns_ops->put(ns);
 out_put_task:
 	put_task_struct(task);
 out:
-	return len;
+	return res;
 }
 
 static const struct inode_operations proc_ns_link_inode_operations = {

fs/proc/self.c

@@ -16,7 +16,7 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 	if (!tgid)
 		return -ENOENT;
 	sprintf(tmp, "%d", tgid);
-	return vfs_readlink(dentry,buffer,buflen,tmp);
+	return readlink_copy(buffer, buflen, tmp);
 }
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)

fs/xfs/xfs_ioctl.c

@@ -271,32 +271,6 @@ xfs_open_by_handle(
 	return error;
 }
 
-/*
- * This is a copy from fs/namei.c:vfs_readlink(), except for removing it's
- * unused first argument.
- */
-STATIC int
-do_readlink(
-	char __user		*buffer,
-	int			buflen,
-	const char		*link)
-{
-        int len;
-
-	len = PTR_ERR(link);
-	if (IS_ERR(link))
-		goto out;
-
-	len = strlen(link);
-	if (len > (unsigned) buflen)
-		len = buflen;
-	if (copy_to_user(buffer, link, len))
-		len = -EFAULT;
- out:
-	return len;
-}
-
-
 int
 xfs_readlink_by_handle(
 	struct file		*parfilp,
@@ -334,7 +308,7 @@ xfs_readlink_by_handle(
 	error = -xfs_readlink(XFS_I(dentry->d_inode), link);
 	if (error)
 		goto out_kfree;
-	error = do_readlink(hreq->ohandle, olen, link);
+	error = readlink_copy(hreq->ohandle, olen, link);
 	if (error)
 		goto out_kfree;
 

include/linux/fs.h

@@ -2517,7 +2517,7 @@ extern const struct file_operations generic_ro_fops;
 
 #define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))
 
-extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
+extern int readlink_copy(char __user *, int, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
 extern void *page_follow_link_light(struct dentry *, struct nameidata *);
 extern void page_put_link(struct dentry *, struct nameidata *, void *);