Patch "net: use skb_to_full_sk() in skb_update_prio()" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    net: use skb_to_full_sk() in skb_update_prio()

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-use-skb_to_full_sk-in-skb_update_prio.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Mar 28 20:16:33 CEST 2018
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 14 Mar 2018 09:04:16 -0700
Subject: net: use skb_to_full_sk() in skb_update_prio()

From: Eric Dumazet <edumazet@google.com>


[ Upstream commit 4dcb31d4649df36297296b819437709f5407059c ]

Andrei Vagin reported a KASAN: slab-out-of-bounds error in
skb_update_prio()

Since SYNACK might be attached to a request socket, we need to
get back to the listener socket.
Since this listener is manipulated without locks, add const
qualifiers to sock_cgroup_prioidx() so that the const can also
be used in skb_update_prio()

Also add the const qualifier to sock_cgroup_classid() for consistency.

Fixes: ca6fb0651883 ("tcp: attach SYNACK messages to request sockets instead of listener")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/cgroup-defs.h |    4 ++--
 net/core/dev.c              |   22 +++++++++++++++-------
 2 files changed, 17 insertions(+), 9 deletions(-)

--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -609,13 +609,13 @@ struct sock_cgroup_data {
  * updaters and return part of the previous pointer as the prioidx or
  * classid.  Such races are short-lived and the result isn't critical.
  */
-static inline u16 sock_cgroup_prioidx(struct sock_cgroup_data *skcd)
+static inline u16 sock_cgroup_prioidx(const struct sock_cgroup_data *skcd)
 {
 	/* fallback to 1 which is always the ID of the root cgroup */
 	return (skcd->is_data & 1) ? skcd->prioidx : 1;
 }
 
-static inline u32 sock_cgroup_classid(struct sock_cgroup_data *skcd)
+static inline u32 sock_cgroup_classid(const struct sock_cgroup_data *skcd)
 {
 	/* fallback to 0 which is the unconfigured default classid */
 	return (skcd->is_data & 1) ? skcd->classid : 0;
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3179,15 +3179,23 @@ static inline int __dev_xmit_skb(struct
 #if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
 static void skb_update_prio(struct sk_buff *skb)
 {
-	struct netprio_map *map = rcu_dereference_bh(skb->dev->priomap);
+	const struct netprio_map *map;
+	const struct sock *sk;
+	unsigned int prioidx;
 
-	if (!skb->priority && skb->sk && map) {
-		unsigned int prioidx =
-			sock_cgroup_prioidx(&skb->sk->sk_cgrp_data);
+	if (skb->priority)
+		return;
+	map = rcu_dereference_bh(skb->dev->priomap);
+	if (!map)
+		return;
+	sk = skb_to_full_sk(skb);
+	if (!sk)
+		return;
 
-		if (prioidx < map->priomap_len)
-			skb->priority = map->priomap[prioidx];
-	}
+	prioidx = sock_cgroup_prioidx(&sk->sk_cgrp_data);
+
+	if (prioidx < map->priomap_len)
+		skb->priority = map->priomap[prioidx];
 }
 #else
 #define skb_update_prio(skb)


Patches currently in stable-queue which might be from edumazet@google.com are

queue-4.9/ipv6-fix-access-to-non-linear-packet-in-ndisc_fill_redirect_hdr_option.patch
queue-4.9/skbuff-fix-not-waking-applications-when-errors-are-enqueued.patch
queue-4.9/l2tp-do-not-accept-arbitrary-sockets.patch
queue-4.9/net-use-skb_to_full_sk-in-skb_update_prio.patch
queue-4.9/ieee802154-6lowpan-fix-possible-null-deref-in-lowpan_device_event.patch