| Message ID | 20231206120923.GA14115@ubuntu (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | appletalk: Fix Use-After-Free in atalk_ioctl | expand |
From: Hyunwoo Kim <v4bel@theori.io> Date: Wed, 6 Dec 2023 04:09:23 -0800 > Because atalk_ioctl() accesses sk->sk_receive_queue > without holding a sk->sk_receive_queue.lock, it can > cause a race with atalk_recvmsg(). > A use-after-free for skb occurs with the following flow. > ``` > atalk_ioctl() -> skb_peek() > atalk_recvmsg() -> skb_recv_datagram() -> skb_free_datagram() > ``` > Add sk->sk_receive_queue.lock to atalk_ioctl() to fix this issue. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Hyunwoo Kim <v4bel@theori.io> > --- > net/appletalk/ddp.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c > index 9ba04a69ec2a..f240d5338bc9 100644 > --- a/net/appletalk/ddp.c > +++ b/net/appletalk/ddp.c > @@ -1775,15 +1775,16 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) > break; > } > case TIOCINQ: { > + long amount = 0; > /* > * These two are safe on a single CPU system as only > * user tasks fiddle here > */ > + spin_lock_irq(&sk->sk_receive_queue.lock); nit: please call spin_lock() after declaring all variables; otherwise checkpatch.pl will complain. > struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); > - long amount = 0; Also, please keep the reverse xmas tree. > - > if (skb) > amount = skb->len - sizeof(struct ddpehdr); > + spin_unlock_irq(&sk->sk_receive_queue.lock); > rc = put_user(amount, (int __user *)argp); > break; > } > -- > 2.25.1 >
diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c index 9ba04a69ec2a..f240d5338bc9 100644 --- a/net/appletalk/ddp.c +++ b/net/appletalk/ddp.c @@ -1775,15 +1775,16 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) break; } case TIOCINQ: { + long amount = 0; /* * These two are safe on a single CPU system as only * user tasks fiddle here */ + spin_lock_irq(&sk->sk_receive_queue.lock); struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); - long amount = 0; - if (skb) amount = skb->len - sizeof(struct ddpehdr); + spin_unlock_irq(&sk->sk_receive_queue.lock); rc = put_user(amount, (int __user *)argp); break; }
Because atalk_ioctl() accesses sk->sk_receive_queue without holding a sk->sk_receive_queue.lock, it can cause a race with atalk_recvmsg(). A use-after-free for skb occurs with the following flow. ``` atalk_ioctl() -> skb_peek() atalk_recvmsg() -> skb_recv_datagram() -> skb_free_datagram() ``` Add sk->sk_receive_queue.lock to atalk_ioctl() to fix this issue. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Hyunwoo Kim <v4bel@theori.io> --- net/appletalk/ddp.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)