xfrm: Fix stack-out-of-bounds with misconfigured transport mode policies.

On policies with a transport mode template, we pass the addresses
from the flowi to xfrm_state_find(), assuming that the IP addresses
(and address family) don't change during transformation.

Unfortunately our policy template validation is not strict enough.
It is possible to configure policies with transport mode template
where the address family of the template does not match the selectors
address family. This lead to stack-out-of-bound reads because
we compare arddesses of the wrong family. Fix this by refusing
such a configuration, address family can not change on transport
mode.

We use the assumption that, on transport mode, the first templates
address family must match the address family of the policy selector.
Subsequent transport mode templates must mach the address family of
the previous template.

Signed-off-by: Steffen Klassert <[email protected]>

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index ff58c37469d694d68c66d7a36c0916387baa3836..bdb48e5dba0480aa4c3c6855be42cfb93f3bf335 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1419,11 +1419,14 @@ static void copy_templates(struct xfrm_policy *xp, struct xfrm_user_tmpl *ut,
 
 static int validate_tmpl(int nr, struct xfrm_user_tmpl *ut, u16 family)
 {
+       u16 prev_family;
        int i;
 
        if (nr > XFRM_MAX_DEPTH)
                return -EINVAL;
 
+       prev_family = family;
+
        for (i = 0; i < nr; i++) {
                /* We never validated the ut->family value, so many
                 * applications simply leave it at zero.  The check was
@@ -1435,6 +1438,12 @@ 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;
+
+               prev_family = ut[i].family;
+
                switch (ut[i].family) {
                case AF_INET:
                        break;