Re: [PATCH - alsa-utils 1/1] arecord: Remove only regular files

From: Takashi Iwai <tiwai@suse.de>
To: "Александр Волков" <a.volkov@rusbitech.ru>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	Arun Raghavan <arun@accosted.net>
Subject: Re: [PATCH - alsa-utils 1/1] arecord: Remove only regular files
Date: Wed, 23 Sep 2015 15:28:46 +0200	[thread overview]
Message-ID: <s5hy4fx6z8x.wl-tiwai@suse.de> (raw)
In-Reply-To: <56016099.30606@rusbitech.ru>

On Tue, 22 Sep 2015 16:07:21 +0200,
Александр Волков wrote:
> 
> 22.09.2015 16:24, Arun Raghavan пишет:
> > On 21 September 2015 at 18:35, Alexander Volkov <a.volkov@rusbitech.ru> wrote:
> >> arecord removes a file before writing into it. It's not
> >> appropriate in some cases. For example, if you a pass
> >> a symlink to a file, then the symlink will be removed
> >> while the user expects to record into the symlink's target.
> >> Another case is recording into the device file. Some
> >> modems provide a tty device file as a voice device.
> >> And it's not possible to write into it under root with
> >> arecord, because it removes the device file.
> >>
> >> So check the type of a file before writing into it and
> >> remove only regular files.
> >>
> >> Signed-off-by: Alexander Volkov <a.volkov@rusbitech.ru>
> >>
> >> diff --git a/aplay/aplay.c b/aplay/aplay.c
> >> index 459f7dd..1b2cdfc 100644
> >> --- a/aplay/aplay.c
> >> +++ b/aplay/aplay.c
> >> @@ -2929,6 +2929,7 @@ static void capture(char *orig_name)
> >>          char *name = orig_name; /* current filename */
> >>          char namebuf[PATH_MAX+1];
> >>          off64_t count, rest;            /* number of bytes to capture */
> >> +       struct stat statbuf;
> >>
> >>          /* get number of bytes to capture */
> >>          count = calc_count();
> >> @@ -2973,7 +2974,10 @@ static void capture(char *orig_name)
> >>                          }
> >>
> >>                          /* open a new file */
> >> -                       remove(name);
> >> +                       if (!lstat(name, &statbuf)) {
> >> +                               if (S_ISREG(statbuf.st_mode))
> >> +                                       remove(name);
> >> +                       }
> >>                          fd = safe_open(name);
> >>                          if (fd < 0) {
> >>                                  perror(name);
> > Would it work to just open with O_TRUNC?
> >
> > -- Arun
> I guess that "remove" is used here to exclude mutual access to the file.
> We can record to the created file while some program may read the 
> removed file.
> Using O_TRUNC will break this use case.

Yeah, it's a good argument.  I applied your patch as is now.

thanks,

Takashi
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