From 5f1810352d4c42ad56de02500b44af9446f05bf5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 14 Apr 2021 12:36:44 -0700 Subject: [PATCH] net/packet: remove data races in fanout operations [ 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 Reported-by: "Gong, Sishuai" Cc: Willem de Bruijn Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- 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 6bbc7a4485938..b6b0024c5fac9 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 baafc3f3fa252..7af1e9179385f 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 { -- 2.47.2