diff mbox series

[5.12,578/677] net/packet: remove data races in fanout operations

Message ID 20210512144856.591873791@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH May 12, 2021, 2:50 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 94f633ea8ade8418634d152ad0931133338226f6 ]

af_packet fanout uses RCU rules to ensure f->arr elements
are not dismantled before RCU grace period.

However, it lacks rcu accessors to make sure KCSAN and other tools
wont detect data races. Stupid compilers could also play games.

Fixes: dc99f600698d ("packet: Add fanout support.")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: "Gong, Sishuai" <sishuai@purdue.edu>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/packet/af_packet.c | 15 +++++++++------
 net/packet/internal.h  |  2 +-
 2 files changed, 10 insertions(+), 7 deletions(-)
diff mbox series

Patch

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e24b2841c643..9611e41c7b8b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1359,7 +1359,7 @@  static unsigned int fanout_demux_rollover(struct packet_fanout *f,
 	struct packet_sock *po, *po_next, *po_skip = NULL;
 	unsigned int i, j, room = ROOM_NONE;
 
-	po = pkt_sk(f->arr[idx]);
+	po = pkt_sk(rcu_dereference(f->arr[idx]));
 
 	if (try_self) {
 		room = packet_rcv_has_room(po, skb);
@@ -1371,7 +1371,7 @@  static unsigned int fanout_demux_rollover(struct packet_fanout *f,
 
 	i = j = min_t(int, po->rollover->sock, num - 1);
 	do {
-		po_next = pkt_sk(f->arr[i]);
+		po_next = pkt_sk(rcu_dereference(f->arr[i]));
 		if (po_next != po_skip && !READ_ONCE(po_next->pressure) &&
 		    packet_rcv_has_room(po_next, skb) == ROOM_NORMAL) {
 			if (i != j)
@@ -1466,7 +1466,7 @@  static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
 	if (fanout_has_flag(f, PACKET_FANOUT_FLAG_ROLLOVER))
 		idx = fanout_demux_rollover(f, skb, idx, true, num);
 
-	po = pkt_sk(f->arr[idx]);
+	po = pkt_sk(rcu_dereference(f->arr[idx]));
 	return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
 }
 
@@ -1480,7 +1480,7 @@  static void __fanout_link(struct sock *sk, struct packet_sock *po)
 	struct packet_fanout *f = po->fanout;
 
 	spin_lock(&f->lock);
-	f->arr[f->num_members] = sk;
+	rcu_assign_pointer(f->arr[f->num_members], sk);
 	smp_wmb();
 	f->num_members++;
 	if (f->num_members == 1)
@@ -1495,11 +1495,14 @@  static void __fanout_unlink(struct sock *sk, struct packet_sock *po)
 
 	spin_lock(&f->lock);
 	for (i = 0; i < f->num_members; i++) {
-		if (f->arr[i] == sk)
+		if (rcu_dereference_protected(f->arr[i],
+					      lockdep_is_held(&f->lock)) == sk)
 			break;
 	}
 	BUG_ON(i >= f->num_members);
-	f->arr[i] = f->arr[f->num_members - 1];
+	rcu_assign_pointer(f->arr[i],
+			   rcu_dereference_protected(f->arr[f->num_members - 1],
+						     lockdep_is_held(&f->lock)));
 	f->num_members--;
 	if (f->num_members == 0)
 		__dev_remove_pack(&f->prot_hook);
diff --git a/net/packet/internal.h b/net/packet/internal.h
index 5f61e59ebbff..48af35b1aed2 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -94,7 +94,7 @@  struct packet_fanout {
 	spinlock_t		lock;
 	refcount_t		sk_ref;
 	struct packet_type	prot_hook ____cacheline_aligned_in_smp;
-	struct sock		*arr[];
+	struct sock	__rcu	*arr[];
 };
 
 struct packet_rollover {