Re: [PATCH][BZ 21357] unwind-dw2-fde: Call free() outside of unwind mutex

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 06/04/2017 16:58, Rabin Vincent wrote:
> From: Rabin Vincent <rabinv@axis.com>
> 
> __deregister_frame_info_bases() calls free() while holding a mutex which
> is also used from _Unwind_Find_FDE().  This leads to a deadlock if
> AddressSanitizer uses _Unwind_Backtrace() from its free()
> implementation.
> 
> 2017-04-06  Rabin Vincent  <rabinv@axis.com>
> 
> 	[BZ #21357]
> 	* sysdeps/generic/unwind-dw2-fde.c (__deregister_frame_info_bases):
> 	Call free() outside of mutex.
> 
> diff --git a/sysdeps/generic/unwind-dw2-fde.c b/sysdeps/generic/unwind-dw2-fde.c
> index 2f0bcd2..104a255 100644
> --- a/sysdeps/generic/unwind-dw2-fde.c
> +++ b/sysdeps/generic/unwind-dw2-fde.c
> @@ -202,6 +202,7 @@ __deregister_frame_info_bases (void *begin)
>  {
>    struct object **p;
>    struct object *ob = 0;
> +  struct fde_vector *tofree = NULL;
>  
>    /* If .eh_frame is empty, we haven't registered.  */
>    if (*(uword *) begin == 0)
> @@ -225,7 +226,7 @@ __deregister_frame_info_bases (void *begin)
>  	  {
>  	    ob = *p;
>  	    *p = ob->next;
> -	    free (ob->u.sort);
> +	    tofree = ob->u.sort;
>  	    goto out;
>  	  }
>        }
> @@ -244,6 +245,7 @@ __deregister_frame_info_bases (void *begin)
>  
>   out:
>    __gthread_mutex_unlock (&object_mutex);
> +  free (tofree);
>    return (void *) ob;
>  }
>  hidden_def (__deregister_frame_info_bases)

LGTM, I assume you actually tested on some platform, right? Do you have write access?