[BZ,21357] unwind-dw2-fde: Call free() outside of unwind mutex
Commit Message
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.
Comments
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?
On Mon, Apr 10, 2017 at 11:40:07AM -0300, Adhemerval Zanella wrote:
> On 06/04/2017 16:58, Rabin Vincent wrote:
> > [BZ #21357]
> > * sysdeps/generic/unwind-dw2-fde.c (__deregister_frame_info_bases):
> > Call free() outside of mutex.
>
> LGTM, I assume you actually tested on some platform, right? Do you have write access?
Yes, I tested it on a 32-bit MIPS platform. No, I don't have write
access.
Thanks.
On 13/04/2017 06:55, Rabin Vincent wrote:
> On Mon, Apr 10, 2017 at 11:40:07AM -0300, Adhemerval Zanella wrote:
>> On 06/04/2017 16:58, Rabin Vincent wrote:
>>> [BZ #21357]
>>> * sysdeps/generic/unwind-dw2-fde.c (__deregister_frame_info_bases):
>>> Call free() outside of mutex.
>>
>> LGTM, I assume you actually tested on some platform, right? Do you have write access?
>
> Yes, I tested it on a 32-bit MIPS platform. No, I don't have write
> access.
>
> Thanks.
>
Alright, I will check this in.
@@ -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)