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

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Message-ID: <ZuHz9lSFY4dWD/4W@pop-os.localdomain>
Date: Wed, 11 Sep 2024 12:48:06 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: Stanislav Fomichev <stfomichev@...il.com>
Cc: Eric Dumazet <edumazet@...gle.com>,
	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 11:49:32AM -0700, Stanislav Fomichev wrote:
> Can you explain what is not correct?
> 
> Calling BPF_CGROUP_RUN_PROG_GETSOCKOPT with max_optlen=0 should not be
> a problem I think? (the buffer simply won't be accessible to the bpf prog)

Sure. Sorry for not providing all the details.

If I understand the behavior of copy_from_user() correctly, it may
return partially copied data in case of error, which then leads to a
partially-copied 'max_optlen'.

So, do you expect a partially-copied max_optlen to be passed to the
eBPF program meanwhile the user still expects a complete one (since no
-EFAULT)?

Thanks.