Skip to content

Commit

Permalink
packet: fix bitfield update race
Browse files Browse the repository at this point in the history 
Updates to the bitfields in struct packet_sock are not atomic.
Serialize these read-modify-write cycles.

Move po->running into a separate variable. Its writes are protected by
po->bind_lock (except for one startup case at packet_create). Also
replace a textual precondition warning with lockdep annotation.

All others are set only in packet_setsockopt. Serialize these
updates by holding the socket lock. Analogous to other field updates,
also hold the lock when testing whether a ring is active (pg_vec).

Fixes: 8dc4194 ("[PACKET]: Add optional checksum computation for recvmsg")
Reported-by: DaeRyong Jeong <threeearcat@gmail.com>
Reported-by: Byoungyoung Lee <byoungyoung@purdue.edu>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
  • Loading branch information
Willem de Bruijn authored and David S. Miller committed Apr 24, 2018
1 parent 9cf2f43 commit a6361f0
Show file tree
Hide file tree
Showing 2 changed files with 49 additions and 21 deletions.
60 changes: 44 additions & 16 deletions net/packet/af_packet.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -329,11 +329,11 @@ static void packet_pick_tx_queue(struct net_device *dev, struct sk_buff *skb)
skb_set_queue_mapping(skb, queue_index);
}

/* register_prot_hook must be invoked with the po->bind_lock held,
/* __register_prot_hook must be invoked through register_prot_hook
* or from a context in which asynchronous accesses to the packet
* socket is not possible (packet_create()).
*/
static void register_prot_hook(struct sock *sk)
static void __register_prot_hook(struct sock *sk)
{
struct packet_sock *po = pkt_sk(sk);

Expand All @@ -348,8 +348,13 @@ static void register_prot_hook(struct sock *sk)
}
}

/* {,__}unregister_prot_hook() must be invoked with the po->bind_lock
* held. If the sync parameter is true, we will temporarily drop
static void register_prot_hook(struct sock *sk)
{
lockdep_assert_held_once(&pkt_sk(sk)->bind_lock);
__register_prot_hook(sk);
}

/* If the sync parameter is true, we will temporarily drop
* the po->bind_lock and do a synchronize_net to make sure no
* asynchronous packet processing paths still refer to the elements
* of po->prot_hook. If the sync parameter is false, it is the
Expand All @@ -359,6 +364,8 @@ static void __unregister_prot_hook(struct sock *sk, bool sync)
{
struct packet_sock *po = pkt_sk(sk);

lockdep_assert_held_once(&po->bind_lock);

po->running = 0;

if (po->fanout)
Expand Down Expand Up @@ -3252,7 +3259,7 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,

if (proto) {
po->prot_hook.type = proto;
register_prot_hook(sk);
__register_prot_hook(sk);
}

mutex_lock(&net->packet.sklist_lock);
Expand Down Expand Up @@ -3732,12 +3739,18 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv

if (optlen != sizeof(val))
return -EINVAL;
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
return -EBUSY;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;
po->tp_loss = !!val;
return 0;

lock_sock(sk);
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
ret = -EBUSY;
} else {
po->tp_loss = !!val;
ret = 0;
}
release_sock(sk);
return ret;
}
case PACKET_AUXDATA:
{
Expand All @@ -3748,7 +3761,9 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;

lock_sock(sk);
po->auxdata = !!val;
release_sock(sk);
return 0;
}
case PACKET_ORIGDEV:
Expand All @@ -3760,7 +3775,9 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;

lock_sock(sk);
po->origdev = !!val;
release_sock(sk);
return 0;
}
case PACKET_VNET_HDR:
Expand All @@ -3769,15 +3786,20 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv

if (sock->type != SOCK_RAW)
return -EINVAL;
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
return -EBUSY;
if (optlen < sizeof(val))
return -EINVAL;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;

po->has_vnet_hdr = !!val;
return 0;
lock_sock(sk);
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
ret = -EBUSY;
} else {
po->has_vnet_hdr = !!val;
ret = 0;
}
release_sock(sk);
return ret;
}
case PACKET_TIMESTAMP:
{
Expand Down Expand Up @@ -3815,11 +3837,17 @@ packet_setsockopt(struct socket *sock, int level, int optname, char __user *optv

if (optlen != sizeof(val))
return -EINVAL;
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec)
return -EBUSY;
if (copy_from_user(&val, optval, sizeof(val)))
return -EFAULT;
po->tp_tx_has_off = !!val;

lock_sock(sk);
if (po->rx_ring.pg_vec || po->tx_ring.pg_vec) {
ret = -EBUSY;
} else {
po->tp_tx_has_off = !!val;
ret = 0;
}
release_sock(sk);
return 0;
}
case PACKET_QDISC_BYPASS:
Expand Down
10 changes: 5 additions & 5 deletions net/packet/internal.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -112,10 +112,12 @@ struct packet_sock {
int copy_thresh;
spinlock_t bind_lock;
struct mutex pg_vec_lock;
unsigned int running:1, /* prot_hook is attached*/
auxdata:1,
unsigned int running; /* bind_lock must be held */
unsigned int auxdata:1, /* writer must hold sock lock */
origdev:1,
has_vnet_hdr:1;
has_vnet_hdr:1,
tp_loss:1,
tp_tx_has_off:1;
int pressure;
int ifindex; /* bound device */
__be16 num;
Expand All @@ -125,8 +127,6 @@ struct packet_sock {
enum tpacket_versions tp_version;
unsigned int tp_hdrlen;
unsigned int tp_reserve;
unsigned int tp_loss:1;
unsigned int tp_tx_has_off:1;
unsigned int tp_tstamp;
struct net_device __rcu *cached_dev;
int (*xmit)(struct sk_buff *skb);
Expand Down

0 comments on commit a6361f0

Please sign in to comment.