Re: [PATCH] xdiff/xmerge: fix memory leak in xdl_merge

From: Patrick Steinhardt <ps@pks.im>
Date: Feb 23, 2016, 11:51 UTC
Message-ID: <20160223115135.GA977@pks-pc.localdomain>
In-Reply-To: <alpine.DEB.2.20.1602231108260.3152@virtualbox>

On Tue, Feb 23, 2016 at 11:09:50AM +0100, Johannes Schindelin wrote:

Show 34 quoted lines

> Hi Patrick,
> 
> On Tue, 23 Feb 2016, Patrick Steinhardt wrote:
> 
> > When building the script for the second file that is to be merged
> > we have already allocated memory for data structures related to
> > the first file. When we encounter an error in building the second
> > script we only free allocated memory related to the second file
> > before erroring out.
> 
> ACK.
> 
> I wonder, though, whether we need this in addition:
> 
> -- snipsnap --
> t a/xdiff/xmerge.c b/xdiff/xmerge.c
> index 625198e..e5c8745 100644
> --- a/xdiff/xmerge.c
> +++ b/xdiff/xmerge.c
> @@ -579,8 +579,11 @@ int xdl_merge(mmfile_t *orig, mmfile_t *mf1, mmfile_t
> *mf2,
>  	result->ptr = NULL;
>  	result->size = 0;
>  
> -	if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0 ||
> -			xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {
> +	if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0) {
> +		return -1;
> +	}
> +	if (xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {
> +		xdl_free_env(&xe1);
>  		return -1;
>  	}
>  	if (xdl_change_compact(&xe1.xdf1, &xe1.xdf2, xpp->flags) < 0 ||

Oh, yes, this is required. I am somewhat confused by all the pointers being passed around there, it is not immediately obvious which pointers are being allocated and which not when you are not intimate with the code base.

So thanks for pointing this out. Will post v2 soon.

Patrick