[Qemu-devel] [PATCH-for-3.1.1 0/1] Backport of CVE-2019-14378 fix

[Qemu-devel] [PATCH-for-3.1.1 0/1] Backport of CVE-2019-14378 fix

[Philippe Mathieu-Daudé]

Trivial backport from the libslirp repository.

Samuel Thibault (1):
  Fix heap overflow in ip_reass on big packet input

 slirp/ip_input.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

-- 
2.20.1

[Qemu-devel] [PATCH-for-3.1.1 1/1] Fix heap overflow in ip_reass on big packet input

[Philippe Mathieu-Daudé]

From: Samuel Thibault <samuel.thibault@ens-lyon.org>

When the first fragment does not fit in the preallocated buffer, q will
already be pointing to the ext buffer, so we mustn't try to update it.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
(cherry picked from libslirp commit 126c04acbabd7ad32c2b018fe10dfac2a3bc1210)
Fixes: CVE-2019-14378
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
 slirp/ip_input.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/slirp/ip_input.c b/slirp/ip_input.c
index 348e1dca5a..07d8808671 100644
--- a/slirp/ip_input.c
+++ b/slirp/ip_input.c
@@ -334,6 +334,8 @@ insert:
     q = fp->frag_link.next;
 	m = dtom(slirp, q);
 
+	int was_ext = m->m_flags & M_EXT;
+
 	q = (struct ipasfrag *) q->ipf_next;
 	while (q != (struct ipasfrag*)&fp->frag_link) {
 	  struct mbuf *t = dtom(slirp, q);
@@ -356,7 +358,7 @@ insert:
 	 * the old buffer (in the mbuf), so we must point ip
 	 * into the new buffer.
 	 */
-	if (m->m_flags & M_EXT) {
+	if (!was_ext && m->m_flags & M_EXT) {
 	  int delta = (char *)q - m->m_dat;
 	  q = (struct ipasfrag *)(m->m_ext + delta);
 	}
-- 
2.20.1

Re: [Qemu-devel] [PATCH-for-3.1.1 1/1] Fix heap overflow in ip_reass on big packet input

[Marc-André Lureau]

On Fri, Aug 2, 2019 at 10:09 PM Philippe Mathieu-Daudé
<philmd@redhat.com> wrote:
>
> From: Samuel Thibault <samuel.thibault@ens-lyon.org>
>
> When the first fragment does not fit in the preallocated buffer, q will
> already be pointing to the ext buffer, so we mustn't try to update it.
>
> Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
> (cherry picked from libslirp commit 126c04acbabd7ad32c2b018fe10dfac2a3bc1210)
> Fixes: CVE-2019-14378
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>


thanks

> ---
>  slirp/ip_input.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/slirp/ip_input.c b/slirp/ip_input.c
> index 348e1dca5a..07d8808671 100644
> --- a/slirp/ip_input.c
> +++ b/slirp/ip_input.c
> @@ -334,6 +334,8 @@ insert:
>      q = fp->frag_link.next;
>         m = dtom(slirp, q);
>
> +       int was_ext = m->m_flags & M_EXT;
> +
>         q = (struct ipasfrag *) q->ipf_next;
>         while (q != (struct ipasfrag*)&fp->frag_link) {
>           struct mbuf *t = dtom(slirp, q);
> @@ -356,7 +358,7 @@ insert:
>          * the old buffer (in the mbuf), so we must point ip
>          * into the new buffer.
>          */
> -       if (m->m_flags & M_EXT) {
> +       if (!was_ext && m->m_flags & M_EXT) {
>           int delta = (char *)q - m->m_dat;
>           q = (struct ipasfrag *)(m->m_ext + delta);
>         }
> --
> 2.20.1
>
>


-- 
Marc-André Lureau