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setipv4sourcefilter: Avoid using alloca.

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Use a scratch_buffer rather than alloca/malloc to avoid potential stack
overflow.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Joe Simmons-Talbott 2023-05-26 09:58:27 -04:00 committed by Siddhesh Poyarekar
parent a363f70751
commit 02f3d4c53a
1 changed files with 7 additions and 17 deletions
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24
sysdeps/unix/sysv/linux/setipv4sourcefilter.c
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@ -16,12 +16,12 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <alloca.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <netinet/in.h>
#include <scratch_buffer.h>
#include <sys/socket.h>
@ -33,17 +33,12 @@ setipv4sourcefilter (int s, struct in_addr interface, struct in_addr group,
/* We have to create an struct ip_msfilter object which we can pass
to the kernel. */
size_t needed = IP_MSFILTER_SIZE (numsrc);
int use_alloca = __libc_use_alloca (needed);
struct ip_msfilter *imsf;
if (use_alloca)
imsf = (struct ip_msfilter *) alloca (needed);
else
{
imsf = (struct ip_msfilter *) malloc (needed);
if (imsf == NULL)
return -1;
}
struct scratch_buffer buf;
scratch_buffer_init (&buf);
if (!scratch_buffer_set_array_size (&buf, 1, needed))
return -1;
struct ip_msfilter *imsf = buf.data;
imsf->imsf_multiaddr = group;
imsf->imsf_interface = interface;
@ -53,12 +48,7 @@ setipv4sourcefilter (int s, struct in_addr interface, struct in_addr group,
int result = __setsockopt (s, SOL_IP, IP_MSFILTER, imsf, needed);
if (! use_alloca)
{
int save_errno = errno;
free (imsf);
__set_errno (save_errno);
}
scratch_buffer_free (&buf);
return result;
}