[alsa-devel] [PATCH] alsactl: Store lockfile in /tmp

[Takashi Iwai]

At Tue, 06 May 2014 16:53:00 +0200,
Jaroslav Kysela wrote:
> 
> Date 6.5.2014 13:57, Julian Scheel wrote:
> > It can not be generally assumed that the directories in which asound.state
> > resides are writable. Instead using /tmp as location for lock files seems more
> > reliable.
> 
> Apart the missing free for the mallocated string and ommiting the TMPDIR
> environment variable, I think that the right directory for global locks
> is /var/lock . The default asound.state directory is now /var/lib/alsa -
> I don't see the benefit.

Agreed.  Above all, using a fixed path with /tmp is really fragile,
easily leading to a security risk for a service that is run by root
like this.

> What's the reason for this change? Perhaps using an environmental
> variable to override the lock path may be more appropriate for a custom
> directory structure.

... or give an option?


Takashi

> 
>                                    Jaroslav
> 
> > 
> > Signed-off-by: Julian Scheel <julian at jusst.de>
> > ---
> >  alsactl/lock.c | 13 ++++++++++---
> >  1 file changed, 10 insertions(+), 3 deletions(-)
> > 
> > diff --git a/alsactl/lock.c b/alsactl/lock.c
> > index 587a109..7ca3a09 100644
> > --- a/alsactl/lock.c
> > +++ b/alsactl/lock.c
> > @@ -36,17 +36,24 @@ static int state_lock_(const char *file, int lock, int timeout)
> >  	struct flock lck;
> >  	struct stat st;
> >  	char lcktxt[12];
> > +	char *filename;
> >  	char *nfile;
> >  
> >  	if (!do_lock)
> >  		return 0;
> > -	nfile = malloc(strlen(file) + 6);
> > +
> > +	/* only use the actual filename, not the path */
> > +	filename = strrchr(file, '/');
> > +	if (!filename)
> > +		filename = file;
> > +
> > +	nfile = malloc(strlen(filename) + 10);
> >  	if (nfile == NULL) {
> >  		error("No enough memory...");
> >  		return -ENOMEM;
> >  	}
> > -	strcpy(nfile, file);
> > -	strcat(nfile, ".lock");
> > +
> > +	sprintf(nfile, "/tmp/%s.lock", filename);
> >  	lck.l_type = lock ? F_WRLCK : F_UNLCK;
> >  	lck.l_whence = SEEK_SET;
> >  	lck.l_start = 0;
> > 
> 
> 
> -- 
> Jaroslav Kysela <perex at perex.cz>
> Linux Kernel Sound Maintainer
> ALSA Project; Red Hat, Inc.
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