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xfrm: refine validation of template and selector families

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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 <daniel@iogearbox.net>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Florian Westphal 2019-01-09 14:37:34 +01:00 committed by Steffen Klassert
parent dd9ee34440
commit 35e6103861
1 changed files with 9 additions and 4 deletions
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13
net/xfrm/xfrm_user.c
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@ -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;