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FAILED: patch "[PATCH] net: use skb_to_full_sk() in skb_update_prio()" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Mar 29, 2018

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The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From 4dcb31d4649df36297296b819437709f5407059c Mon Sep 17 00:00:00 2001

From: Eric Dumazet <[email protected]>
Date: Wed, 14 Mar 2018 09:04:16 -0700
Subject: [PATCH] net: use skb_to_full_sk() in skb_update_prio()

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 <[email protected]>
Reported-by Andrei Vagin <[email protected]>
Signed-off-by David S. Miller <[email protected]>
include/linux/cgroup-defs.h +2 -2
index 9f242b876fde..f8e76d01a5ad 100644
@@ -755,13 +755,13 @@ 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;
net/core/dev.c +15 -7
index 2cedf520cb28..12be20535714 100644
@@ -3278,15 +3278,23 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 #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)