netdev - Re: [PATCH v2] net/rose: Fix Use-After-Free in rose

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Message-ID: <CANn89i+MuoTwc2A_BfKYcvrJ1vECJ+EVUtYiHLVfO_AFcg7Big@mail.gmail.com>
Date: Wed, 6 Dec 2023 11:56:53 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Hyunwoo Kim <v4bel@...ori.io>
Cc: ralf@...ux-mips.org, imv4bel@...il.com, davem@...emloft.net, 
	kuba@...nel.org, pabeni@...hat.com, linux-hams@...r.kernel.org, 
	netdev@...r.kernel.org
Subject: Re: [PATCH v2] net/rose: Fix Use-After-Free in rose_ioctl

On Wed, Dec 6, 2023 at 11:52 AM Hyunwoo Kim <v4bel@...ori.io> wrote:
>
> Dear,
>
> On Wed, Dec 06, 2023 at 11:33:15AM +0100, Eric Dumazet wrote:
> > On Wed, Dec 6, 2023 at 5:13 AM Hyunwoo Kim <v4bel@...ori.io> wrote:
> > >
> > > Because rose_ioctl() accesses sk->sk_receive_queue
> > > without holding a sk->sk_receive_queue.lock, it can
> > > cause a race with rose_accept().
> > > A use-after-free for skb occurs with the following flow.
> > > ```
> > > rose_ioctl() -> skb_peek()
> > > rose_accept() -> skb_dequeue() -> kfree_skb()
> > > ```
> > > Add sk->sk_receive_queue.lock to rose_ioctl() to fix this issue.
> > >
> >
> > Please add a Fixes: tag
> >
> > > Signed-off-by: Hyunwoo Kim <v4bel@...ori.io>
> > > ---
> > > v1 -> v2: Use sk->sk_receive_queue.lock instead of lock_sock.
> > > ---
> > >  net/rose/af_rose.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c
> > > index 0cc5a4e19900..841c238de222 100644
> > > --- a/net/rose/af_rose.c
> > > +++ b/net/rose/af_rose.c
> > > @@ -1316,8 +1316,10 @@ static int rose_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
> > >                 struct sk_buff *skb;
> > >                 long amount = 0L;
> > >                 /* These two are safe on a single CPU system as only user tasks fiddle here */
> > > +               spin_lock(&sk->sk_receive_queue.lock);
> >
> > You need interrupt safety here.
> >
> > sk_receive_queue can be fed from interrupt, that would potentially deadlock.
>
> I want to change spin_lock to spin_lock_irqsave, is this okay?


Either spin_lock_irq() or spin_lock_irqsave() will work.

>
>
> Regards,
> Hyunwoo Kim
>
> >
> > >                 if ((skb = skb_peek(&sk->sk_receive_queue)) != NULL)
> > >                         amount = skb->len;
> > > +               spin_unlock(&sk->sk_receive_queue.lock);
> > >                 return put_user(amount, (unsigned int __user *) argp);
> > >         }
> > >
> > > --
> > > 2.25.1
> > >