Return-Path: From: Sasha Levin To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Steffen Klassert , Sasha Levin Subject: [PATCH AUTOSEL 4.14 11/61] xfrm: Fix NULL pointer dereference when skb_dst_force clears the dst_entry. Date: Tue, 16 Oct 2018 00:13:13 -0400 Message-Id: <20181016041403.135678-11-sashal@kernel.org> In-Reply-To: <20181016041403.135678-1-sashal@kernel.org> References: <20181016041403.135678-1-sashal@kernel.org> List-ID: From: Steffen Klassert [ 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 Reported-by: Kristian Evensen Reported-by: Wolfgang Walter Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- 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)) { -- 2.17.1