From 9d84284cc83ba9429f1f9064fe42f74c988d37e8 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Wed, 9 Jan 2019 14:37:34 +0100 Subject: xfrm: refine validation of template and selector families commit 35e6103861a3a970de6c84688c6e7a1f65b164ca upstream. The check assumes that in transport mode, the first templates family must match the address family of the policy selector. Syzkaller managed to build a template using MODE_ROUTEOPTIMIZATION, with ipv4-in-ipv6 chain, leading to following splat: BUG: KASAN: stack-out-of-bounds in xfrm_state_find+0x1db/0x1854 Read of size 4 at addr ffff888063e57aa0 by task a.out/2050 xfrm_state_find+0x1db/0x1854 xfrm_tmpl_resolve+0x100/0x1d0 xfrm_resolve_and_create_bundle+0x108/0x1000 [..] Problem is that addresses point into flowi4 struct, but xfrm_state_find treats them as being ipv6 because it uses templ->encap_family is used (AF_INET6 in case of reproducer) rather than family (AF_INET). This patch inverts the logic: Enforce 'template family must match selector' EXCEPT for tunnel and BEET mode. In BEET and Tunnel mode, xfrm_tmpl_resolve_one will have remote/local address pointers changed to point at the addresses found in the template, rather than the flowi ones, so no oob read will occur. Reported-by: 3ntr0py1337@gmail.com Reported-by: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: Steffen Klassert Signed-off-by: Greg Kroah-Hartman --- net/xfrm/xfrm_user.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) (limited to 'net/xfrm') diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c index 566919838d5e..ab557827aac0 100644 --- a/net/xfrm/xfrm_user.c +++ b/net/xfrm/xfrm_user.c @@ -1488,10 +1488,15 @@ static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family) if (!ut[i].family) ut[i].family = family; - if ((ut[i].mode == XFRM_MODE_TRANSPORT) && - (ut[i].family != prev_family)) - return -EINVAL; - + switch (ut[i].mode) { + case XFRM_MODE_TUNNEL: + case XFRM_MODE_BEET: + break; + default: + if (ut[i].family != prev_family) + return -EINVAL; + break; + } if (ut[i].mode >= XFRM_MODE_MAX) return -EINVAL; -- cgit v1.2.3