4.19-stable review patch. If anyone has any objections, please let me know. ------------------ [ 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 <jpmenil@xxxxxxxxx> Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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 be3520e429c9..790b514f86b6 100644 --- a/net/xfrm/xfrm_input.c +++ b/net/xfrm/xfrm_input.c @@ -346,6 +346,12 @@ 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); @@ -385,7 +391,6 @@ 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