linux-kernel - Re: [PATCH] soundwire: sysfs_emit() expects a buffer of size PAGE

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Message-ID: <CAMCbnuYVELzWU0jZm8LcSEVRigOz+P1Fmk9suunr63asFjMFiQ@mail.gmail.com>
Date: Fri, 25 Jul 2025 12:22:16 -0600
From: Sergio Pérez <sperezglz@...il.com>
To: Vinod Koul <vkoul@...nel.org>
Cc: Takashi Iwai <tiwai@...e.de>, yung-chuan.liao@...ux.intel.com, 
	pierre-louis.bossart@...ux.dev, linux-sound@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soundwire: sysfs_emit() expects a buffer of size PAGE_SIZE

All right, then, this will be handled with a different approach.

Thanks,
Sergio

El jue, 24 jul 2025 a la(s) 3:52 a.m., Vinod Koul (vkoul@...nel.org) escribió:
>
> On 24-07-25, 09:19, Takashi Iwai wrote:
> > On Thu, 24 Jul 2025 01:09:25 +0200,
> > Sergio Perez Gonzalez wrote:
> > >
> > > In read_buffer_show(), allocate sufficient memory to pass on to
> > > sysfs_emit(), which expects a buffer of size PAGE_SIZE.
> > >
> > > Link: https://scan7.scan.coverity.com/#/project-view/53936/11354?selectedIssue=1648019
> > > Fixes: 35323d8ab811 ("soundwire: replace scnprintf() with sysfs_emit() for sysfs consistency")
> > > Signed-off-by: Sergio Perez Gonzalez <sperezglz@...il.com>
> > > ---
> > >  drivers/soundwire/debugfs.c | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/soundwire/debugfs.c b/drivers/soundwire/debugfs.c
> > > index 825f7abbad32..08fb1e29026e 100644
> > > --- a/drivers/soundwire/debugfs.c
> > > +++ b/drivers/soundwire/debugfs.c
> > > @@ -306,12 +306,12 @@ static int cmd_go(void *data, u64 value)
> > >  DEFINE_DEBUGFS_ATTRIBUTE(cmd_go_fops, NULL,
> > >                      cmd_go, "%llu\n");
> > >
> > > -#define MAX_LINE_LEN 128
> > > -
> > >  static int read_buffer_show(struct seq_file *s_file, void *data)
> > >  {
> > > -   char buf[MAX_LINE_LEN];
> > >     int i;
> > > +   char *buf __free(kfree) = kzalloc(PAGE_SIZE, GFP_KERNEL);
> > > +   if (!buf)
> > > +           return -ENOMEM;
> >
> > IMO, it's better to scratch the whole previous change.
> > It makes little sense to allocate a large buffer here just for the
> > temporary formatting.
> >
> > Moreover, *_show() functions there take seq_file pointer, and you can
> > just use seq_printf() directly.  The sysfs/kobject show callback is
> > with the a fixed PAGE_SIZE buffer, hence sysfs_emit() is useful, but
> > in this case, it's a completely different story.
>
> Agree, dropped now!
>
> --
> ~Vinod