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af_packet: fix tracking issues in packet_do_bind() 

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2096377

commit bf44077c1b3ae86668bce02d9466e7134a6569ec
Author: Eric Dumazet <edumazet@google.com>
Date:   Fri Jan 7 10:39:53 2022 -0800

    af_packet: fix tracking issues in packet_do_bind()

    It appears that my changes in packet_do_bind() were
    slightly wrong.

    syzbot found that calling bind() twice would trigger
    a false positive.

    Remove proto_curr/dev_curr variables and rewrite things
    to be less confusing (like not having to use netdev_tracker_alloc(),
    and instead use the standard dev_hold_track())

    Fixes: f1d9268e0618 ("net: add net device refcount tracker to struct packet_type")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Link: https://lore.kernel.org/r/20220107183953.3886647-1-eric.dumazet@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
This commit is contained in:
Ivan Vecera 2022-06-13 18:39:17 +02:00
parent 66a3ba4495
commit 23c617e70c
1 changed files with 8 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
net/packet/af_packet.c
View File

@ -3146,12 +3146,10 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
__be16 proto)
{
struct packet_sock *po = pkt_sk(sk);
struct net_device *dev_curr;
__be16 proto_curr;
bool need_rehook;
struct net_device *dev = NULL;
int ret = 0;
bool unlisted = false;
bool need_rehook;
int ret = 0;
lock_sock(sk);
spin_lock(&po->bind_lock);
@ -3176,14 +3174,10 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
}
}
dev_hold(dev);
proto_curr = po->prot_hook.type;
dev_curr = po->prot_hook.dev;
need_rehook = proto_curr != proto || dev_curr != dev;
need_rehook = po->prot_hook.type != proto || po->prot_hook.dev != dev;
if (need_rehook) {
dev_hold(dev);
if (po->running) {
rcu_read_unlock();
/* prevents packet_notifier() from calling
@ -3192,7 +3186,6 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
WRITE_ONCE(po->num, 0);
__unregister_prot_hook(sk, true);
rcu_read_lock();
dev_curr = po->prot_hook.dev;
if (dev)
unlisted = !dev_get_by_index_rcu(sock_net(sk),
dev->ifindex);
@ -3202,25 +3195,21 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
WRITE_ONCE(po->num, proto);
po->prot_hook.type = proto;
dev_put_track(dev_curr, &po->prot_hook.dev_tracker);
dev_curr = NULL;
dev_put_track(po->prot_hook.dev, &po->prot_hook.dev_tracker);
if (unlikely(unlisted)) {
dev_put(dev);
po->prot_hook.dev = NULL;
WRITE_ONCE(po->ifindex, -1);
packet_cached_dev_reset(po);
} else {
if (dev)
netdev_tracker_alloc(dev,
&po->prot_hook.dev_tracker,
GFP_ATOMIC);
dev_hold_track(dev, &po->prot_hook.dev_tracker,
GFP_ATOMIC);
po->prot_hook.dev = dev;
WRITE_ONCE(po->ifindex, dev ? dev->ifindex : 0);
packet_cached_dev_assign(po, dev);
}
dev_put(dev);
}
dev_put_track(dev_curr, &po->prot_hook.dev_tracker);
if (proto == 0 || !need_rehook)
goto out_unlock;