From: David Laight <David.Laight@ACULAB.COM>
To: 'Marcelo Ricardo Leitner' <marcelo.leitner@gmail.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-sctp@vger.kernel.org" <linux-sctp@vger.kernel.org>,
Neil Horman <nhorman@tuxdriver.com>
Subject: RE: [PATCH net-next] sctp: Pull the user copies out of the individual sockopt functions.
Date: Thu, 21 May 2020 07:32:14 +0000 [thread overview]
Message-ID: <e777874fbd0e4ccb813e08145f3c3359@AcuMS.aculab.com> (raw)
In-Reply-To: <20200521001725.GW2491@localhost.localdomain>
From: 'Marcelo Ricardo Leitner'
> Sent: 21 May 2020 01:17
> On Wed, May 20, 2020 at 03:08:13PM +0000, David Laight wrote:
> ...
> > Only SCTP_SOCKOPT_CONNECTX3 contains an indirect pointer.
> > It is also the only getsockopt() that wants to return a buffer
> > and an error code. It is also definitely abusing getsockopt().
> ...
> > @@ -1375,11 +1350,11 @@ struct compat_sctp_getaddrs_old {
> > #endif
> >
> > static int sctp_getsockopt_connectx3(struct sock *sk, int len,
> > - char __user *optval,
> > - int __user *optlen)
> > + struct sctp_getaddrs_old *param,
> > + int *optlen)
> > {
> > - struct sctp_getaddrs_old param;
> > sctp_assoc_t assoc_id = 0;
> > + struct sockaddr *addrs;
> > int err = 0;
> >
> > #ifdef CONFIG_COMPAT
..
> > } else
> > #endif
> > {
> > - if (len < sizeof(param))
> > + if (len < sizeof(*param))
> > return -EINVAL;
> > - if (copy_from_user(¶m, optval, sizeof(param)))
> > - return -EFAULT;
> > }
> >
> > - err = __sctp_setsockopt_connectx(sk, (struct sockaddr __user *)
> > - param.addrs, param.addr_num,
> > + addrs = memdup_user(param->addrs, param->addr_num);
>
> I'm staring at this for a while now but I don't get this memdup_user.
> AFAICT, params->addrs is not __user anymore here, because
> sctp_getsockopt() copied the whole thing already, no?
> Also weird because it is being called from kernel_sctp_getsockopt(),
> which now has no knowledge of __user buffers.
> Maybe I didn't get something from the patch description.
The connectx3 sockopt buffer contains a pointer to the user buffer
that contains the actual addresses.
So a second copy_from_user() is needed.
This does mean that this option can only be actioned from userspace.
Kernel code can get the same functionality using one of the
other interfaces to connectx().
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-05-21 7:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 15:08 [PATCH net-next] sctp: Pull the user copies out of the individual sockopt functions David Laight
2020-05-20 23:33 ` kbuild test robot
2020-05-21 0:17 ` 'Marcelo Ricardo Leitner'
2020-05-21 7:32 ` David Laight [this message]
2020-05-21 14:36 ` 'Marcelo Ricardo Leitner'
2020-05-21 15:37 ` 'Marcelo Ricardo Leitner'
2020-05-21 15:39 ` Christoph Hellwig
2020-05-21 15:52 ` David Laight
2020-05-21 16:09 ` David Laight
2020-05-21 16:45 ` 'Marcelo Ricardo Leitner'
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