[FFmpeg-devel] [PATCH 1/2] avcodec/v4l2_m2m: Avoid using intermediate buffer

[Andriy Gelman]

On Tue, 10. Mar 06:37, Andreas Rheinhardt wrote:
> Andreas Rheinhardt:
> > Up until now, v4l2_m2m would write via snprintf() into an intermediate
> > buffer and then copy from there (via strncpy()) to the end buffer. This
> > commit changes this by removing the intermediate buffer.
> > 
> > The call to strncpy() was actually of the form strncpy(dst, src,
> > strlen(src) + 1) which is unsafe in general, but safe in this instance
> > because dst and src were both of the same size and src was a proper
> > zero-terminated string. But this nevertheless led to a compiler warning
> > "‘strncpy’ specified bound depends on the length of the source argument
> > [-Wstringop-overflow=]" in GCC 9.2. strlen() was unnecessary anyway.
> > 
> > Reviewed-by: Andriy Gelman <andriy.gelman at gmail.com>
> > Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> > ---
> > Thanks to Andriy for testing and reviewing.
> > 
> >  libavcodec/v4l2_m2m.c | 8 +++-----
> >  1 file changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/libavcodec/v4l2_m2m.c b/libavcodec/v4l2_m2m.c
> > index 2d21f910bc..e48b3a8ccf 100644
> > --- a/libavcodec/v4l2_m2m.c
> > +++ b/libavcodec/v4l2_m2m.c
> > @@ -358,7 +358,6 @@ int ff_v4l2_m2m_codec_init(V4L2m2mPriv *priv)
> >  {
> >      int ret = AVERROR(EINVAL);
> >      struct dirent *entry;
> > -    char node[PATH_MAX];
> >      DIR *dirp;
> >  
> >      V4L2m2mContext *s = priv->context;
> > @@ -372,9 +371,8 @@ int ff_v4l2_m2m_codec_init(V4L2m2mPriv *priv)
> >          if (strncmp(entry->d_name, "video", 5))
> >              continue;
> >  
> > -        snprintf(node, sizeof(node), "/dev/%s", entry->d_name);
> > -        av_log(s->avctx, AV_LOG_DEBUG, "probing device %s\n", node);
> > -        strncpy(s->devname, node, strlen(node) + 1);
> > +        snprintf(s->devname, sizeof(s->devname), "/dev/%s", entry->d_name);
> > +        av_log(s->avctx, AV_LOG_DEBUG, "probing device %s\n", s->devname);
> >          ret = v4l2_probe_driver(s);
> >          if (!ret)
> >              break;
> > @@ -389,7 +387,7 @@ int ff_v4l2_m2m_codec_init(V4L2m2mPriv *priv)
> >          return ret;
> >      }
> >  
> > -    av_log(s->avctx, AV_LOG_INFO, "Using device %s\n", node);
> > +    av_log(s->avctx, AV_LOG_INFO, "Using device %s\n", s->devname);
> >  
> >      return v4l2_configure_contexts(s);
> >  }
> > 
> 
> Ping for this patchset.
> 
> - Andreas
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lgtm

Thanks,
-- 
Andriy