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 --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 {