lkml.org 
[lkml]   [2019]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH AUTOSEL 4.9 02/32] xfrm: refine validation of template and selector families
Date
From: Florian Westphal <fw@strlen.de>

[ Upstream commit 35e6103861a3a970de6c84688c6e7a1f65b164ca ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/xfrm/xfrm_user.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 026770884d46b..f6f91c3b2de02 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1408,10 +1408,15 @@ 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;

--
2.19.1
\
 
 \ /
  Last update: 2019-02-23 22:18    [W:0.099 / U:8.536 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site