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authorNikolay Aleksandrov <nikolay@cumulusnetworks.com>2018-11-16 18:50:01 +0200
committerDavid S. Miller <davem@davemloft.net>2018-11-17 21:38:44 -0800
commit9d332e69c1dc74dcd748de7cbd2dac5c61bda265 (patch)
tree912c15036f8f473ddbf7526c4c9b4763c18f164f /net
parent95506588d2c1d72ca29adef8ae9bf771bcfb4ced (diff)
net: bridge: fix vlan stats use-after-free on destruction
Syzbot reported a use-after-free of the global vlan context on port vlan destruction. When I added per-port vlan stats I missed the fact that the global vlan context can be freed before the per-port vlan rcu callback. There're a few different ways to deal with this, I've chosen to add a new private flag that is set only when per-port stats are allocated so we can directly check it on destruction without dereferencing the global context at all. The new field in net_bridge_vlan uses a hole. v2: cosmetic change, move the check to br_process_vlan_info where the other checks are done v3: add change log in the patch, add private (in-kernel only) flags in a hole in net_bridge_vlan struct and use that instead of mixing user-space flags with private flags Fixes: 9163a0fc1f0c ("net: bridge: add support for per-port vlan stats") Reported-by: syzbot+04681da557a0e49a52e5@syzkaller.appspotmail.com Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/bridge/br_private.h7
-rw-r--r--net/bridge/br_vlan.c3
2 files changed, 9 insertions, 1 deletions
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 2920e06a5403..04c19a37e500 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -102,12 +102,18 @@ struct br_tunnel_info {
struct metadata_dst *tunnel_dst;
};
+/* private vlan flags */
+enum {
+ BR_VLFLAG_PER_PORT_STATS = BIT(0),
+};
+
/**
* struct net_bridge_vlan - per-vlan entry
*
* @vnode: rhashtable member
* @vid: VLAN id
* @flags: bridge vlan flags
+ * @priv_flags: private (in-kernel) bridge vlan flags
* @stats: per-cpu VLAN statistics
* @br: if MASTER flag set, this points to a bridge struct
* @port: if MASTER flag unset, this points to a port struct
@@ -127,6 +133,7 @@ struct net_bridge_vlan {
struct rhash_head tnode;
u16 vid;
u16 flags;
+ u16 priv_flags;
struct br_vlan_stats __percpu *stats;
union {
struct net_bridge *br;
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 8c9297a01947..e84be08b8285 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -197,7 +197,7 @@ static void nbp_vlan_rcu_free(struct rcu_head *rcu)
v = container_of(rcu, struct net_bridge_vlan, rcu);
WARN_ON(br_vlan_is_master(v));
/* if we had per-port stats configured then free them here */
- if (v->brvlan->stats != v->stats)
+ if (v->priv_flags & BR_VLFLAG_PER_PORT_STATS)
free_percpu(v->stats);
v->stats = NULL;
kfree(v);
@@ -264,6 +264,7 @@ static int __vlan_add(struct net_bridge_vlan *v, u16 flags)
err = -ENOMEM;
goto out_filt;
}
+ v->priv_flags |= BR_VLFLAG_PER_PORT_STATS;
} else {
v->stats = masterv->stats;
}