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From 7babaac5d49ee7a88a5a324668dd13b575635d09 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 14 Feb 2017 09:03:51 -0800
Subject: [PATCH] packet: fix races in fanout_add()
[ Upstream commit d199fab63c11998a602205f7ee7ff7c05c97164b ]
Multiple threads can call fanout_add() at the same time.
We need to grab fanout_mutex earlier to avoid races that could
lead to one thread freeing po->rollover that was set by another thread.
Do the same in fanout_release(), for peace of mind, and to help us
finding lockdep issues earlier.
CVE: CVE-2017-6346
Upstream-Status: Backport
Fixes: dc99f600698d ("packet: Add fanout support.")
Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
net/packet/af_packet.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 4cd7e27..88cec95 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1447,13 +1447,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
return -EINVAL;
}
+ mutex_lock(&fanout_mutex);
+
+ err = -EINVAL;
if (!po->running)
- return -EINVAL;
+ goto out;
+ err = -EALREADY;
if (po->fanout)
- return -EALREADY;
+ goto out;
- mutex_lock(&fanout_mutex);
match = NULL;
list_for_each_entry(f, &fanout_list, list) {
if (f->id == id &&
@@ -1509,17 +1512,16 @@ static void fanout_release(struct sock *sk)
struct packet_sock *po = pkt_sk(sk);
struct packet_fanout *f;
- f = po->fanout;
- if (!f)
- return;
-
mutex_lock(&fanout_mutex);
- po->fanout = NULL;
+ f = po->fanout;
+ if (f) {
+ po->fanout = NULL;
- if (atomic_dec_and_test(&f->sk_ref)) {
- list_del(&f->list);
- dev_remove_pack(&f->prot_hook);
- kfree(f);
+ if (atomic_dec_and_test(&f->sk_ref)) {
+ list_del(&f->list);
+ dev_remove_pack(&f->prot_hook);
+ kfree(f);
+ }
}
mutex_unlock(&fanout_mutex);
}
--
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