[PATCH 4.9 08/28] net: use skb_to_full_sk() in skb_update_prio()

Greg Kroah-Hartman
2018-03-29T18:00:27Z

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)