Re: [PATCH] malloc: preserve errno on mcheck hooks [BZ #17924]

["H.J. Lu" <hjl.tools@gmail.com>]

On Tue, Dec 29, 2020 at 12:24 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
>
> Similar to the fix 69fda43b8d, save and restore errno for the hook
> functions used for MALLOC_CHECK_=3.
>
> It fixes the malloc/tst-free-errno-mcheck regression.
>
> Checked on x86_64-linux-gnu.
> ---
>  malloc/hooks.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/malloc/hooks.c b/malloc/hooks.c
> index 6474ba8b38..fc285f15c6 100644
> --- a/malloc/hooks.c
> +++ b/malloc/hooks.c
> @@ -260,6 +260,8 @@ free_check (void *mem, const void *caller)
>    if (!mem)
>      return;
>
> +  int err = errno;
> +
>  #ifdef USE_MTAG
>    /* Quickly check that the freed pointer matches the tag for the memory.
>       This gives a useful double-free detection.  */
> @@ -274,12 +276,16 @@ free_check (void *mem, const void *caller)
>      {
>        __libc_lock_unlock (main_arena.mutex);
>        munmap_chunk (p);
> -      return;
>      }
> -  /* Mark the chunk as belonging to the library again.  */
> -  (void)TAG_REGION (chunk2rawmem (p), CHUNK_AVAILABLE_SIZE (p) - CHUNK_HDR_SZ);
> -  _int_free (&main_arena, p, 1);
> -  __libc_lock_unlock (main_arena.mutex);
> +  else
> +    {
> +      /* Mark the chunk as belonging to the library again.  */
> +      (void)TAG_REGION (chunk2rawmem (p), CHUNK_AVAILABLE_SIZE (p)
> +                                         - CHUNK_HDR_SZ);
> +      _int_free (&main_arena, p, 1);
> +      __libc_lock_unlock (main_arena.mutex);
> +    }
> +  __set_errno (err);
>  }
>
>  static void *
> --
> 2.25.1
>

LGTM.

Thanks.

-- 
H.J.