From: Eric Dumazet <edumazet@google.com>
Date: Wed, 18 Oct 2017 16:14:52 -0700
Subject: packet: avoid panic in packet_getsockopt()
Patch-mainline: v4.14-rc6
Git-commit: 509c7a1ecc8601f94ffba8a00889fefb239c00c6
References: bsc#1076830
syzkaller got crashes in packet_getsockopt() processing
PACKET_ROLLOVER_STATS command while another thread was managing
to change po->rollover
Using RCU will fix this bug. We might later add proper RCU annotations
for sparse sake.
In v2: I replaced kfree(rollover) in fanout_add() to kfree_rcu()
variant, as spotted by John.
Fixes: a9b6391814d5 ("packet: rollover statistics")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: John Sperbeck <jsperbeck@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
net/packet/af_packet.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 65f63250bdb8..c4bc46e112ac 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1772,7 +1772,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags)
out:
if (err && rollover) {
- kfree(rollover);
+ kfree_rcu(rollover, rcu);
po->rollover = NULL;
}
mutex_unlock(&fanout_mutex);
@@ -1799,8 +1799,10 @@ static struct packet_fanout *fanout_release(struct sock *sk)
else
f = NULL;
- if (po->rollover)
+ if (po->rollover) {
kfree_rcu(po->rollover, rcu);
+ po->rollover = NULL;
+ }
}
mutex_unlock(&fanout_mutex);
@@ -3861,6 +3863,7 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
void *data = &val;
union tpacket_stats_u st;
struct tpacket_rollover_stats rstats;
+ struct packet_rollover *rollover;
if (level != SOL_PACKET)
return -ENOPROTOOPT;
@@ -3939,13 +3942,18 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
0);
break;
case PACKET_ROLLOVER_STATS:
- if (!po->rollover)
+ rcu_read_lock();
+ rollover = rcu_dereference(po->rollover);
+ if (rollover) {
+ rstats.tp_all = atomic_long_read(&rollover->num);
+ rstats.tp_huge = atomic_long_read(&rollover->num_huge);
+ rstats.tp_failed = atomic_long_read(&rollover->num_failed);
+ data = &rstats;
+ lv = sizeof(rstats);
+ }
+ rcu_read_unlock();
+ if (!rollover)
return -EINVAL;
- rstats.tp_all = atomic_long_read(&po->rollover->num);
- rstats.tp_huge = atomic_long_read(&po->rollover->num_huge);
- rstats.tp_failed = atomic_long_read(&po->rollover->num_failed);
- data = &rstats;
- lv = sizeof(rstats);
break;
case PACKET_TX_HAS_OFF:
val = po->tp_tx_has_off;
--
2.15.1