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authorEric Dumazet <edumazet@google.com>2017-10-19 02:14:52 +0300
committerDavid S. Miller <davem@davemloft.net>2017-10-21 03:51:34 +0300
commit509c7a1ecc8601f94ffba8a00889fefb239c00c6 (patch)
treef9dcb3f8a8782f6c6bbc6231e9eea2382146d36b
parentc92e8c02fe664155ac4234516e32544bec0f113d (diff)
downloadlinux-509c7a1ecc8601f94ffba8a00889fefb239c00c6.tar.xz
packet: avoid panic in packet_getsockopt()
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>
-rw-r--r--net/packet/af_packet.c24
1 files changed, 16 insertions, 8 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index bec01a3daf5b..2986941164b1 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1769,7 +1769,7 @@ 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);
@@ -1796,8 +1796,10 @@ 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);
@@ -3851,6 +3853,7 @@ 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;
@@ -3929,13 +3932,18 @@ 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;