Commit 509c7a1e authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

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: a9b63918 ("packet: rollover statistics")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: John Sperbeck <jsperbeck@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c92e8c02
......@@ -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;
......
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