[PATCH 4.14-stable] xfrm: Fix a race in the xdst pcpu cache.

[Steffen Klassert]

commit 76a4201191814a0061cb5c861fafb9ecaa764846 upstream.

We need to run xfrm_resolve_and_create_bundle() with
bottom halves off. Otherwise we may reuse an already
released dst_enty when the xfrm lookup functions are
called from process context.

Fixes: c30d78c14a813db39a647b6a348b428 ("xfrm: add xdst pcpu cache")
Reported-by: Darius Ski <darius....@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klass...@secunet.com>
---
 net/xfrm/xfrm_policy.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index bc5eae12fb09..bd6b0e7a0ee4 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2063,8 +2063,11 @@ xfrm_bundle_lookup(struct net *net, const struct flowi 
*fl, u16 family, u8 dir,
        if (num_xfrms <= 0)
                goto make_dummy_bundle;
 
+       local_bh_disable();
        xdst = xfrm_resolve_and_create_bundle(pols, num_pols, fl, family,
-                                                 xflo->dst_orig);
+                                             xflo->dst_orig);
+       local_bh_enable();
+
        if (IS_ERR(xdst)) {
                err = PTR_ERR(xdst);
                if (err != -EAGAIN)
@@ -2151,9 +2154,12 @@ struct dst_entry *xfrm_lookup(struct net *net, struct 
dst_entry *dst_orig,
                                goto no_transform;
                        }
 
+                       local_bh_disable();
                        xdst = xfrm_resolve_and_create_bundle(
                                        pols, num_pols, fl,
                                        family, dst_orig);
+                       local_bh_enable();
+
                        if (IS_ERR(xdst)) {
                                xfrm_pols_put(pols, num_pols);
                                err = PTR_ERR(xdst);
-- 
2.14.1