Re: f2fs: avoid abnormal behavior on broken symlink

[Dan Carpenter <dan.carpenter@oracle.com>]

On Wed, Apr 22, 2015 at 02:28:22PM +0800, Chao Yu wrote:
> > > fs/f2fs/namei.c
> > >    299  static void *f2fs_follow_link(struct dentry *dentry, struct nameidata *nd)
> > >    300  {
> > >    301          struct page *page;
> > >    302
> > >    303          page = page_follow_link_light(dentry, nd);
> > >    304          if (IS_ERR(page))
> > >                            ^^^^
> > > The code in page_follow_link_light() is a bit hard to follow but it
> > > returns NULL on error.
> 
> I try to find out the other callers' error handling method for
> page_follow_link_light, and it shows all of them use the "IS_ERR" one.
> 
> In page_follow_link_light I also can't find a path which will return a NULL value.
> 
> So, Dan, is that report from smatch not true? or I made a mistake? If so, please
> correct me.

Smatch is correct, it returns NULL on error.  However, I agree that it
looks like it is supposed to return an ERR_PTR.  Every caller seems to
expect that.

I suspect the right fix is to change page_follow_link_light().  But I
don't know this code very well so I just sent the bug report instead of
fixing it myself.  :)

regards,
dan carpenter

diff --git a/fs/namei.c b/fs/namei.c
index ffab2e0..5ca251e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4473,7 +4473,12 @@ EXPORT_SYMBOL(page_readlink);
 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
 {
 	struct page *page = NULL;
-	nd_set_link(nd, page_getlink(dentry, &page));
+	char *link;
+
+	link = page_getlink(dentry, &page);
+	if (IS_ERR(link))
+		return link;
+	nd_set_link(nd, link);
 	return page;
 }
 EXPORT_SYMBOL(page_follow_link_light);

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