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

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Message-ID: <20180124091324.qevb4pawv5dk2z2i@gauss3.secunet.de>
Date:   Wed, 24 Jan 2018 10:13:25 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>, <stable@...r.kernel.org>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH 4.14-stable] xfrm: Fix a race in the xdst pcpu cache.

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.ski@...il.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.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