7127235: (fs) NPE in Files.walkFileTree if cached attributes are GC'ed

[Rémi Forax]

On 01/05/2012 04:04 PM, Alan Bateman wrote:
>
> This is a faux pas in the implementation of Files.walkFileTree. Where 
> the attributes of the files in a directory are read as part of the 
> iteration then they are cached, via a weak reference, to avoid 
> re-fetching them. Unfortunately this code doesn't check if the 
> reference has been cleared which can be lead to a NPE as per the bug 
> report. The fix is to trivially check if the reference has been 
> cleared. This one is really hard to reproduce and I don't have a 
> reliable test case.
>
> -Alan
>
> diff --git a/src/share/classes/java/nio/file/FileTreeWalker.java 
> b/src/share/classes/java/nio/file/FileTreeWalker.java
> --- a/src/share/classes/java/nio/file/FileTreeWalker.java
> +++ b/src/share/classes/java/nio/file/FileTreeWalker.java
> @@ -92,7 +92,7 @@ class FileTreeWalker {
>              (System.getSecurityManager() == null))
>          {
>              BasicFileAttributes cached = 
> ((BasicFileAttributesHolder)file).get();
> -            if (!followLinks || !cached.isSymbolicLink())
> +            if (cached != null && (!followLinks || 
> !cached.isSymbolicLink()))
>                  attrs = cached;
>          }
>          IOException exc = null;
>

Looks Ok for me but I was not able to read the bug report (not available).

cheers,
Rémi