netdev - [PATCH 6/9] xfrm: Fix infinite loop in xfrm_get_dst

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Date:   Tue, 13 Mar 2018 08:09:50 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH 6/9] xfrm: Fix infinite loop in xfrm_get_dst_nexthop with transport mode.

On transport mode we forget to fetch the child dst_entry
before we continue the while loop, this leads to an infinite
loop. Fix this by fetching the child dst_entry before we
continue the while loop.

Fixes: 0f6c480f23f4 ("xfrm: Move dst->path into struct xfrm_dst")
Reported-by: syzbot+7d03c810e50aaedef98a@...kaller.appspotmail.com
Tested-by: Florian Westphal <fw@...len.de>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
 net/xfrm/xfrm_policy.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 150d46633ce6..625b3fca5704 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -2732,14 +2732,14 @@ static const void *xfrm_get_dst_nexthop(const struct dst_entry *dst,
 	while (dst->xfrm) {
 		const struct xfrm_state *xfrm = dst->xfrm;
 
+		dst = xfrm_dst_child(dst);
+
 		if (xfrm->props.mode == XFRM_MODE_TRANSPORT)
 			continue;
 		if (xfrm->type->flags & XFRM_TYPE_REMOTE_COADDR)
 			daddr = xfrm->coaddr;
 		else if (!(xfrm->type->flags & XFRM_TYPE_LOCAL_COADDR))
 			daddr = &xfrm->id.daddr;
-
-		dst = xfrm_dst_child(dst);
 	}
 	return daddr;
 }
-- 
2.14.1