[alsa-devel] [PATCH] aplay: fix lurking capture file overwrite bug

[Takashi Iwai]

On Thu, 14 Apr 2016 06:32:46 +0200,
David Fries wrote:
> 
> If -d was given to arecord while commit
> 8aa13eec80eac312e4b99423909387660fb99b8f (now reverted) was in effect,
> the last read would be shorter than the chunk size, but pcm_read would
> read and return the chunk size, the samples were discarded, and
> capture() continued in a loop because count never reached 0.  arecord
> opens a new file each loop iteration, if arecord is dynamically naming
> files, --use-strftime option or beyond the wave 2GB limit, this will
> generate a series of header only wave files.  If the file is unique
> the originally recorded data is lost and it will continue overwriting
> the same file with a header only wave file.
> 
> While the current pcm_read can't fail (it can exit), it is better to
> just fix this lurking bug in case it is "fixed" again.
> ---
> In my case I wanted to record for 16 hours, I did get the audio, but I
> also found I had 3.1 million 44 byte files, which took the system
> 3 hours to unlink, I'm glad I at least discovered this problem the
> next day..  Debian has the effectively broken pcm_read, after figuring
> out what was going wrong, and that the current arecord doesn't exhibit
> the problem I wanted to fix it anyway.  There are remaining problems,
> pcm_read will read chunk_size, but if the requested size is smaller
> samples are lost, I'm not trying to fix that here.  This will at least
> gracefully close a wave file (update the counts) if read or write
> returns a size different from requested.

Applied, thanks.


Takashi

> 
>  aplay/aplay.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/aplay/aplay.c b/aplay/aplay.c
> index 7acaa83..2da7dda 100644
> --- a/aplay/aplay.c
> +++ b/aplay/aplay.c
> @@ -3067,11 +3067,14 @@ static void capture(char *orig_name)
>  			size_t c = (rest <= (off64_t)chunk_bytes) ?
>  				(size_t)rest : chunk_bytes;
>  			size_t f = c * 8 / bits_per_frame;
> -			if (pcm_read(audiobuf, f) != f)
> +			if (pcm_read(audiobuf, f) != f) {
> +				in_aborting = 1;
>  				break;
> +			}
>  			if (write(fd, audiobuf, c) != c) {
>  				perror(name);
> -				prg_exit(EXIT_FAILURE);
> +				in_aborting = 1;
> +				break;
>  			}
>  			count -= c;
>  			rest -= c;
> @@ -3091,7 +3094,7 @@ static void capture(char *orig_name)
>  		}
>  
>  		if (in_aborting)
> -			break;
> +			prg_exit(EXIT_FAILURE);
>  
>  		/* repeat the loop when format is raw without timelimit or
>  		 * requested counts of data are recorded
> -- 
> 2.1.4
> 
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