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

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Message-ID: <CANn89iKhbQ1wDq1aJyTiZ-yW1Hm-BrKq4V5ihafebEgvWvZe2w@mail.gmail.com>
Date: Wed, 11 Sep 2024 09:13:31 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Qianqiang Liu <qianqiang.liu@....com>
Cc: xiyou.wangcong@...il.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 7:06 AM Qianqiang Liu <qianqiang.liu@....com> wrote:
>
> We must check the return value of the copy_from_sockptr. Otherwise, it
> may cause some weird issues.

What issues precisely ?

I do not think it matters, because the copy is performed later, with
all the needed checks.

eg :

if (copy_from_sockptr(&len, optlen, sizeof(int)))
    return -EFAULT;
...
len = min_t(unsigned int, sizeof(int), len);
if (copy_to_sockptr(optlen, &len, sizeof(int)))
    return -EFAULT;
if (copy_to_sockptr(optval, &val, len))
    return -EFAULT;
return 0;


>
> Signed-off-by: Qianqiang Liu <qianqiang.liu@....com>
> ---
>  net/socket.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/socket.c b/net/socket.c
> index 0a2bd22ec105..6b9a414d01d5 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -2370,8 +2370,11 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level,
>         if (err)
>                 return err;
>
> -       if (!compat)
> -               copy_from_sockptr(&max_optlen, optlen, sizeof(int));
> +       if (!compat) {
> +               err = copy_from_sockptr(&max_optlen, optlen, sizeof(int));
> +               if (err)
> +                       return -EFAULT;
> +       }
>
>         ops = READ_ONCE(sock->ops);
>         if (level == SOL_SOCKET) {
> --
> 2.39.2
>