This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH][BZ 21357] unwind-dw2-fde: Call free() outside of unwind mutex
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Mon, 10 Apr 2017 11:40:07 -0300
- Subject: Re: [PATCH][BZ 21357] unwind-dw2-fde: Call free() outside of unwind mutex
- Authentication-results: sourceware.org; auth=none
- References: <1491508681-30385-1-git-send-email-rabin.vincent@axis.com>
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?