4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ Upstream commit 509c7a1ecc8601f94ffba8a00889fefb239c00c6 ]
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@xxxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Cc: John Sperbeck <jsperbeck@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/packet/af_packet.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1724,7 +1724,7 @@ static int fanout_add(struct sock *sk, u
out:
if (err && rollover) {
- kfree(rollover);
+ kfree_rcu(rollover, rcu);
po->rollover = NULL;
}
mutex_unlock(&fanout_mutex);
@@ -1751,8 +1751,10 @@ static struct packet_fanout *fanout_rele
else
f = NULL;
- if (po->rollover)
+ if (po->rollover) {
kfree_rcu(po->rollover, rcu);
+ po->rollover = NULL;
+ }
}
mutex_unlock(&fanout_mutex);
@@ -3769,6 +3771,7 @@ static int packet_getsockopt(struct sock
void *data = &val;
union tpacket_stats_u st;
struct tpacket_rollover_stats rstats;
+ struct packet_rollover *rollover;
if (level != SOL_PACKET)
return -ENOPROTOOPT;
@@ -3847,13 +3850,18 @@ static int packet_getsockopt(struct sock
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;