| Message ID | 20231209095552.GA406496@v4bel-B760M-AORUS-ELITE-AX (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v2] appletalk: Fix Use-After-Free in atalk_ioctl | expand |
On Sat, 2023-12-09 at 04:55 -0500, Hyunwoo Kim wrote: > 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> > --- > v1 -> v2: Change the code style > --- > net/appletalk/ddp.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c > index 9ba04a69ec2a..016b8fb7f096 100644 > --- a/net/appletalk/ddp.c > +++ b/net/appletalk/ddp.c > @@ -1775,15 +1775,17 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) > break; > } > case TIOCINQ: { > + long amount = 0; > + struct sk_buff *skb; Please, respect the reverse xmas tree order: no one-off exceptions even in this period of the year (pun intended ;) > /* > * These two are safe on a single CPU system as only > * user tasks fiddle here > */ Please remove the now obsoleted comment above. Cheers, Paolo
diff --git a/net/appletalk/ddp.c b/net/appletalk/ddp.c index 9ba04a69ec2a..016b8fb7f096 100644 --- a/net/appletalk/ddp.c +++ b/net/appletalk/ddp.c @@ -1775,15 +1775,17 @@ static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg) break; } case TIOCINQ: { + long amount = 0; + struct sk_buff *skb; /* * These two are safe on a single CPU system as only * user tasks fiddle here */ - struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); - long amount = 0; - + spin_lock_irq(&sk->sk_receive_queue.lock); + skb = skb_peek(&sk->sk_receive_queue); 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> --- v1 -> v2: Change the code style --- net/appletalk/ddp.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)