Commit 73c6f860 authored by Steffen Klassert's avatar Steffen Klassert Committed by Greg Kroah-Hartman

xfrm: Fix NULL pointer dereference when skb_dst_force clears the dst_entry.

[ Upstream commit 9e143793 ]

Since commit 222d7dbd ("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: 222d7dbd ("net: prevent dst uses after free")
Reported-by: default avatarTobias Hommel <netdev-list@genoetigt.de>
Reported-by: default avatarKristian Evensen <kristian.evensen@gmail.com>
Reported-by: default avatarWolfgang Walter <linux@stwm.de>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 35507aab
......@@ -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);
......
......@@ -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)) {
......
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