From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.14 11/59] xfrm: Fix NULL pointer dereference in xfrm_input when skb_dst_force clears the dst_entry. Date: Wed, 26 Dec 2018 17:37:51 -0500 Message-ID: <20181226223839.150262-11-sashal@kernel.org> References: <20181226223839.150262-1-sashal@kernel.org> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: Steffen Klassert , Sasha Levin , netdev@vger.kernel.org To: stable@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20181226223839.150262-1-sashal@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Steffen Klassert [ Upstream commit 0152eee6fc3b84298bb6a79961961734e8afa5b8 ] Since commit 222d7dbd258d ("net: prevent dst uses after free") skb_dst_force() might clear the dst_entry attached to the skb. The xfrm code doesn'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 case the dst_entry was cleared. We also move the skb_dst_force() to a codepath that is not used when the transformation was offloaded, because in this case we don't have a dst_entry attached to the skb. The output and forwarding path was already fixed by commit 9e1437937807 ("xfrm: Fix NULL pointer dereference when skb_dst_force clears the dst_entry.") Fixes: 222d7dbd258d ("net: prevent dst uses after free") Reported-by: Jean-Philippe Menil Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/xfrm/xfrm_input.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c index 8e75319dd9c0..06dec32503bd 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -341,6 +341,12 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) skb->sp->xvec[skb->sp->len++] = x; + skb_dst_force(skb); + if (!skb_dst(skb)) { + XFRM_INC_STATS(net, LINUX_MIB_XFRMINERROR); + goto drop; + } + lock: spin_lock(&x->lock); @@ -380,7 +386,6 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type) XFRM_SKB_CB(skb)->seq.input.low = seq; XFRM_SKB_CB(skb)->seq.input.hi = seq_hi; - skb_dst_force(skb); dev_hold(skb->dev); if (crypto_done) -- 2.19.1