RE: [PATCH 1/1] libctf: Fix double free in ctf_link_add_cu_mapping.

["Willgerodt, Felix" <felix.willgerodt@intel.com>]

> -----Original Message-----
> From: Alan Modra <amodra@gmail.com>
> Sent: Donnerstag, 8. Dezember 2022 02:23
> To: Willgerodt, Felix <felix.willgerodt@intel.com>
> Cc: binutils@sourceware.org
> Subject: Re: [PATCH 1/1] libctf: Fix double free in ctf_link_add_cu_mapping.
> 
> On Wed, Dec 07, 2022 at 03:11:37PM +0100, Felix Willgerodt via Binutils
> wrote:
> > This fixes a potential double free which can occur if we jump to
> > oom_noerrno after the first free.
> >
> > I am not very familiar with libctf, so any comments are welcome.
> > I am wondering if the right solution wouldn't be to free both t and f before
> > the "return 0".  But I didn't fully understand the code and saw that other
> > users of ctf_dynhash_insert() also don't free the key manually.
> 
> No, they can't be freed if successfully inserted into the hash table,
> but "t" should indeed be freed if already inserted.  I'm applying the
> following fix.
> 
> 	* ctf-link.c (ctf_link_add_cu_mapping): Set t NULL after free.
> 
> diff --git a/libctf/ctf-link.c b/libctf/ctf-link.c
> index 702f2b4d5fe..902b4408cd6 100644
> --- a/libctf/ctf-link.c
> +++ b/libctf/ctf-link.c
> @@ -431,7 +431,10 @@ ctf_link_add_cu_mapping (ctf_dict_t *fp, const char
> *from, const char *to)
>  	}
>      }
>    else
> -    free (t);
> +    {
> +      free (t);
> +      t = NULL;
> +    }
> 
>    if (ctf_dynhash_insert (one_out, f, NULL) < 0)
>      {
> 
> 
> --
> Alan Modra
> Australia Development Lab, IBM

Thanks, that looks fine to me as well.

Felix
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