linux-kernel - Re: [PATCH 1/1] nfsd: incorrect check for debugfs returns

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Date:	Wed, 25 Mar 2015 11:08:56 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Jeff Layton <jeff.layton@...marydata.com>
Cc:	Chengyu Song <csong84@...ech.edu>, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, taesoo@...ech.edu,
	changwoo@...ech.edu, sanidhya@...ech.edu, blee@...ech.edu
Subject: Re: [PATCH 1/1] nfsd: incorrect check for debugfs returns

On Tue, Mar 24, 2015 at 06:44:20AM -0400, Jeff Layton wrote:
> On Mon, 23 Mar 2015 22:58:05 -0400
> Chengyu Song <csong84@...ech.edu> wrote:
> 
> > debugfs_create_dir and debugfs_create_file may return -ENODEV when debugfs
> > is not configured, so the return value should be checked against ERROR_VALUE
> > as well, otherwise the later dereference of the dentry pointer would crash
> > the kernel.
> > 
> > Signed-off-by: Chengyu Song <csong84@...ech.edu>
> > ---
> >  fs/nfsd/fault_inject.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> > 
> > diff --git a/fs/nfsd/fault_inject.c b/fs/nfsd/fault_inject.c
> > index c16bf5a..621d065 100644
> > --- a/fs/nfsd/fault_inject.c
> > +++ b/fs/nfsd/fault_inject.c
> > @@ -132,19 +132,23 @@ int nfsd_fault_inject_init(void)
> >  	unsigned int i;
> >  	struct nfsd_fault_inject_op *op;
> >  	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
> > +	struct dentry *dent;
> >  
> > -	debug_dir = debugfs_create_dir("nfsd", NULL);
> > -	if (!debug_dir)
> > +	dent = debugfs_create_dir("nfsd", NULL);
> > +	if (IS_ERR_OR_NULL(dent))
> >  		goto fail;
> > +	debug_dir = dent;
> >  
> >  	for (i = 0; i < NUM_INJECT_OPS; i++) {
> >  		op = &inject_ops[i];
> > -		if (!debugfs_create_file(op->file, mode, debug_dir, op, &fops_nfsd))
> > +		dent = debugfs_create_file(op->file, mode, debug_dir, op, &fops_nfsd);
> > +		if (IS_ERR_OR_NULL(dent))
> >  			goto fail;
> > +
> >  	}
> >  	return 0;
> >  
> >  fail:
> >  	nfsd_fault_inject_cleanup();
> > -	return -ENOMEM;
> > +	return dent ? PTR_ERR(dent) : -ENOMEM;
> >  }
> 
> No objection to taking this patch in the near term if it helps, but we
> had discussed over the summer just removing the NFS fault injection
> framework.
> 
> Bruce, any objections to making that happen for v4.1?

I was prepared to, but I think Redhat QA people told me that they do use
it--which means other people may too, so I'm sort of reluctant to tear
it out even if it's imperfect.

--b.
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