Received-SPF: pass (google.com: domain of linux-kernel+bounces-137075-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Precedence: bulk
MIME-Version: 1.0
References: <7cf0848b-f44c-42ad-848a-369a249bff77@gmail.com> <tencent_88401767377846C9736D0363C96C23BB4405@qq.com>
In-Reply-To: <tencent_88401767377846C9736D0363C96C23BB4405@qq.com>
From: Eric Dumazet <edumazet@google.com>
Date: Tue, 9 Apr 2024 16:17:42 +0200
Message-ID: <CANn89iJAyCKbL1Gx9mbBMuEvDB7nr-Ao6vB7KbtOK5D0UhiQNQ@mail.gmail.com>
Subject: Re: [PATCH] net/socket: Ensure length of input socket option param >= sizeof(int)
To: Edward Adam Davis <eadavis@qq.com>
Cc: eric.dumazet@gmail.com, johan.hedberg@gmail.com, 
	linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, 
	luiz.dentz@gmail.com, marcel@holtmann.org, netdev@vger.kernel.org, 
	pmenzel@molgen.mpg.de, syzbot+d4ecae01a53fd9b42e7d@syzkaller.appspotmail.com, 
	syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tue, Apr 9, 2024 at 4:02=E2=80=AFPM Edward Adam Davis <eadavis@qq.com> w=
rote:
>
> On Tue, 9 Apr 2024 15:07:41 +0200, Eric Dumazet wrote:
> > > The optlen value passed by syzbot to _sys_setsockopt() is 2, which re=
sults in
> > > only 2 bytes being allocated when allocating memory to kernel_optval,=
 and the
> > > optval size passed when calling the function copy_from_sockptr() is 4=
 bytes.
> > > Here, optlen is determined uniformly in the entry function __sys_sets=
ockopt().
> > > If its value is less than 4, the parameter is considered invalid.
> > >
> > > Reported-by: syzbot+837ba09d9db969068367@syzkaller.appspotmail.com
> > > Reported-by: syzbot+b71011ec0a23f4d15625@syzkaller.appspotmail.com
> > > Reported-by: syzbot+d4ecae01a53fd9b42e7d@syzkaller.appspotmail.com
> > > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> >
> >
> > I think I gave my feedback already.
> >
> > Please do not ignore maintainers feedback.
> >
> > This patch is absolutely wrong.
> >
> > Some setsockopt() deal with optlen =3D=3D 1 just fine, thank you very m=
uch.
> It's better to use evidence to support your claim, rather than your "main=
tainer" title.

I will answer since you ask so nicely,
but if you plan sending linux kernel patches, I suggest you look in
the source code.

Look at do_ip_setsockopt(), which is one of the most used setsockopt()
in the world.

The code is at least 20 years old.

It even supports optlen =3D=3D 0

               if (optlen >=3D sizeof(int)) {
                       if (copy_from_sockptr(&val, optval, sizeof(val)))
                               return -EFAULT;
               } else if (optlen >=3D sizeof(char)) {
                       unsigned char ucval;

                       if (copy_from_sockptr(&ucval, optval, sizeof(ucval))=
)
                               return -EFAULT;
                       val =3D (int) ucval;
               }
       }

       /* If optlen=3D=3D0, it is equivalent to val =3D=3D 0 */