linux-kernel - Re: [PATCH] net: check the return value of the copy_from

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Message-ID: <ZuHMHFovurDNkAIB@pop-os.localdomain>
Date: Wed, 11 Sep 2024 09:58:04 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Qianqiang Liu <qianqiang.liu@....com>, davem@...emloft.net,
	kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: check the return value of the copy_from_sockptr

On Wed, Sep 11, 2024 at 11:12:24AM +0200, Eric Dumazet wrote:
> On Wed, Sep 11, 2024 at 10:23 AM Qianqiang Liu <qianqiang.liu@....com> wrote:
> >
> > > I do not think it matters, because the copy is performed later, with
> > > all the needed checks.
> >
> > No, there is no checks at all.
> >
> 
> Please elaborate ?
> Why should maintainers have to spend time to provide evidence to
> support your claims ?
> Have you thought about the (compat) case ?
> 
> There are plenty of checks. They were there before Stanislav commit.
> 
> Each getsockopt() handler must perform the same actions.


But in line 2379 we have ops->getsockopt==NULL case:

2373         if (!compat)
2374                 copy_from_sockptr(&max_optlen, optlen, sizeof(int));
2375
2376         ops = READ_ONCE(sock->ops);
2377         if (level == SOL_SOCKET) {
2378                 err = sk_getsockopt(sock->sk, level, optname, optval, optlen);
2379         } else if (unlikely(!ops->getsockopt)) {
2380                 err = -EOPNOTSUPP; 	// <--- HERE
2381         } else {
2382                 if (WARN_ONCE(optval.is_kernel || optlen.is_kernel,
2383                               "Invalid argument type"))
2384                         return -EOPNOTSUPP;
2385
2386                 err = ops->getsockopt(sock, level, optname, optval.user,
2387                                       optlen.user);
2388         }

where we simply continue with calling BPF_CGROUP_RUN_PROG_GETSOCKOPT()
which actually needs the 'max_optlen' we copied via copy_from_sockptr().

Do I miss anything here?

Thanks.