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

[James Almer]

On 3/10/2020 3:11 PM, Andriy Gelman wrote:
> 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,

Applied patch 1/2, which i assume is the one you approved.