4.14-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 9e1437937807b0122e8da1ca8765be2adca9aee6 ]
Since commit 222d7dbd258d ("net: prevent dst uses after free") skb_dst_force() might clear the dst_entry attached to the skb. The xfrm code don't expect this to happen, so we crash with a NULL pointer dereference in this case. Fix it by checking skb_dst(skb) for NULL after skb_dst_force() and drop the packet in cast the dst_entry was cleared.
Fixes: 222d7dbd258d ("net: prevent dst uses after free") Reported-by: Tobias Hommel netdev-list@genoetigt.de Reported-by: Kristian Evensen kristian.evensen@gmail.com Reported-by: Wolfgang Walter linux@stwm.de Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xfrm/xfrm_output.c | 4 ++++ net/xfrm/xfrm_policy.c | 4 ++++ 2 files changed, 8 insertions(+)
diff --git a/net/xfrm/xfrm_output.c b/net/xfrm/xfrm_output.c index 35610cc881a9..c47660fba498 100644 --- a/net/xfrm/xfrm_output.c +++ b/net/xfrm/xfrm_output.c @@ -101,6 +101,10 @@ static int xfrm_output_one(struct sk_buff *skb, int err) spin_unlock_bh(&x->lock);
skb_dst_force(skb); + if (!skb_dst(skb)) { + XFRM_INC_STATS(net, LINUX_MIB_XFRMOUTERROR); + goto error_nolock; + }
if (xfrm_offload(skb)) { x->type_offload->encap(x, skb); diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 2fb7a78308e1..37c32e73aaef 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -2550,6 +2550,10 @@ int __xfrm_route_forward(struct sk_buff *skb, unsigned short family) }
skb_dst_force(skb); + if (!skb_dst(skb)) { + XFRM_INC_STATS(net, LINUX_MIB_XFRMFWDHDRERROR); + return 0; + }
dst = xfrm_lookup(net, skb_dst(skb), &fl, NULL, XFRM_LOOKUP_QUEUE); if (IS_ERR(dst)) {