Re: [PATCH/rfc v2] NFS: introduce NFS namespaces.

["NeilBrown" <neilb@suse.de>]

On Thu, 08 Jul 2021, Daire Byrne wrote:
> On Wed, 7 Jul 2021 at 22:25, NeilBrown <neilb@suse.de> wrote:
> >
> > That's pretty solid evidence!
> >
> > I just realized that the stack trace you reported mentions
> > "kfree_const()".
> > My latest patch doesn't include that, and nfs doesn't use it at all.
> > Might you still be using the older patch?
> >
> > NeilBrown
> 
> Oh... the last stack trace, the readdir one? I don't see kfree_const
> myself but I may have a case of word blindness. The first one I
> reported definitely has kfree_const but after your latest patch, this
> last one around readdir doesn't seem to?
> 
> I'm pretty sure I have your latest patch (with kfree instead of
> kfree_const) correctly applied. Though, I will double check that the
> correct kernel and modules were then installed properly on my test VM.

sorry - my bad..

I think I've found it.  Rather than sending the whole patch, here is the
incremental fix.  But not clearing this pointer, I risk the value in it
being freed twice.  That might lead to what you saw.

Thanks,
NeilBrown



diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index 7c644a31d304..9e34af223ce6 100644
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -1451,6 +1451,7 @@ static int nfs_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
 	ctx->nfs_server.export_path	= NULL;
 	ctx->nfs_server.hostname	= NULL;
 	ctx->fscache_uniq		= NULL;
+	ctx->namespace			= NULL;
 	ctx->clone_data.fattr		= NULL;
 	fc->fs_private = ctx;
 	return 0;