[PATCH] getsourcefilter: Get rid of alloca.
Adhemerval Zanella Netto
adhemerval.zanella@linaro.org
Wed May 31 12:27:30 GMT 2023
On 30/05/23 15:13, Joe Simmons-Talbott via Libc-alpha wrote:
> Use a scratch_buffer rather than alloca to avoid potential stack
> overflows.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> sysdeps/unix/sysv/linux/getsourcefilter.c | 24 +++++++----------------
> 1 file changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/sysdeps/unix/sysv/linux/getsourcefilter.c b/sysdeps/unix/sysv/linux/getsourcefilter.c
> index b9ba58c23a..461ad889a9 100644
> --- a/sysdeps/unix/sysv/linux/getsourcefilter.c
> +++ b/sysdeps/unix/sysv/linux/getsourcefilter.c
> @@ -16,10 +16,10 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> -#include <alloca.h>
> #include <assert.h>
> #include <errno.h>
> #include <stdlib.h>
> +#include <scratch_buffer.h>
> #include <string.h>
> #include <stdint.h>
> #include <netatalk/at.h>
> @@ -95,17 +95,12 @@ getsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
> /* We have to create an struct ip_msfilter object which we can pass
> to the kernel. */
> socklen_t needed = GROUP_FILTER_SIZE (*numsrc);
> - int use_alloca = __libc_use_alloca (needed);
>
> - struct group_filter *gf;
> - if (use_alloca)
> - gf = (struct group_filter *) alloca (needed);
> - else
> - {
> - gf = (struct group_filter *) malloc (needed);
> - if (gf == NULL)
> - return -1;
> - }
> + struct scratch_buffer buf;
> + scratch_buffer_init (&buf);
> + if (!scratch_buffer_set_array_size (&buf, 1, needed))
> + return -1;
> + struct group_filter *gf = buf.data;
>
> gf->gf_interface = interface;
> memcpy (&gf->gf_group, group, grouplen);
> @@ -135,12 +130,7 @@ getsourcefilter (int s, uint32_t interface, const struct sockaddr *group,
> }
> }
>
> - if (! use_alloca)
> - {
> - int save_errno = errno;
> - free (gf);
> - __set_errno (save_errno);
> - }
> + scratch_buffer_free (&buf);
>
> return result;
> }
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