linux-kernel - Re: [PATCH v3] remoteproc: Fix NULL vs IS_ERR() checking in rproc_create_trace

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Message-ID: <YeXuOwm3yJW2gnSE@builder.lan>
Date:   Mon, 17 Jan 2022 16:31:23 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Miaoqian Lin <linmq006@...il.com>, linux-kernel@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, ohad@...ery.com
Subject: Re: [PATCH v3] remoteproc: Fix NULL vs IS_ERR() checking in
 rproc_create_trace_file

On Mon 17 Jan 11:06 CST 2022, Mathieu Poirier wrote:

> On Wed, Jan 05, 2022 at 01:10:22PM +0000, Miaoqian Lin wrote:
> > The debugfs_create_file() function doesn't return NULL.
> > It returns error pointers. Fix check in rproc_create_trace_file
> > and make it returns return error pointers.
> 
> s/"returns return"/return
> 
> > Fix check in rproc_handle_trace to propagate the error code.
> > 
> > Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> > ---
> > Changes in v2:
> > - return PTR_ERR(tfile) in rproc_create_trace_file
> > - fix check in rproc_handle_trace()
> > Changes in v3:
> > - return tfile to fix incorrect return type in v2
> > ---
> >  drivers/remoteproc/remoteproc_core.c    | 6 ++++--
> >  drivers/remoteproc/remoteproc_debugfs.c | 4 +---
> >  2 files changed, 5 insertions(+), 5 deletions(-)
> >
> 
> I will fix the above, add a proper "Fixes" tag and apply this patch to
> rproc-next when v5.17-rc1 comes out next week.
> 

We're actually not supposed to check debugfs_create_*() for errors.

> Thanks,
> Mathieu
> 
> > diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> > index 775df165eb45..5608408f8eac 100644
> > --- a/drivers/remoteproc/remoteproc_core.c
> > +++ b/drivers/remoteproc/remoteproc_core.c
> > @@ -656,6 +656,7 @@ static int rproc_handle_trace(struct rproc *rproc, void *ptr,
> >  	struct rproc_debug_trace *trace;
> >  	struct device *dev = &rproc->dev;
> >  	char name[15];
> > +	int ret;
> >  
> >  	if (sizeof(*rsc) > avail) {
> >  		dev_err(dev, "trace rsc is truncated\n");
> > @@ -684,9 +685,10 @@ static int rproc_handle_trace(struct rproc *rproc, void *ptr,
> >  
> >  	/* create the debugfs entry */
> >  	trace->tfile = rproc_create_trace_file(name, rproc, trace);
> > -	if (!trace->tfile) {
> > +	if (IS_ERR(trace->tfile)) {
> > +		ret = PTR_ERR(trace->tfile);
> >  		kfree(trace);
> > -		return -EINVAL;
> > +		return ret;


And actually catching and propagating the error here means that we will
start failing rproc_boot() for firmware including a RSC_TRACE when
debugfs is disabled...

So if we really want to save the heap space we should at least cleanly
ignore the error, by cleaning up and returning 0 here.

> >  	}
> >  
> >  	list_add_tail(&trace->node, &rproc->traces);
> > diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
> > index b5a1e3b697d9..2ae59a365b7e 100644
> > --- a/drivers/remoteproc/remoteproc_debugfs.c
> > +++ b/drivers/remoteproc/remoteproc_debugfs.c
> > @@ -390,10 +390,8 @@ struct dentry *rproc_create_trace_file(const char *name, struct rproc *rproc,
> >  
> >  	tfile = debugfs_create_file(name, 0400, rproc->dbg_dir, trace,
> >  				    &trace_rproc_ops);
> > -	if (!tfile) {
> > +	if (IS_ERR(tfile))
> >  		dev_err(&rproc->dev, "failed to create debugfs trace entry\n");

And I therefor think this function would be better reduced to:

	return debugfs_create_file(...);

Regards,
Bjorn

> > -		return NULL;
> > -	}
> >  
> >  	return tfile;
> >  }
> > -- 
> > 2.17.1
> >