linux-kernel - Re: [PATCH v2 4/5] ipc: Clamp msgmni and shmmni to the real IPCMNI limit

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Message-ID: <20180228010100.GA14069@wotan.suse.de>
Date:   Wed, 28 Feb 2018 01:01:00 +0000
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v2 4/5] ipc: Clamp msgmni and shmmni to the real IPCMNI
 limit

On Tue, Feb 27, 2018 at 03:49:50PM -0500, Waiman Long wrote:
> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
> index 8ad93c2..e4ab272 100644
> --- a/ipc/ipc_sysctl.c
> +++ b/ipc/ipc_sysctl.c
> @@ -41,12 +41,17 @@ static int proc_ipc_dointvec(struct ctl_table *table, int write,
>  static int proc_ipc_dointvec_minmax(struct ctl_table *table, int write,
>  	void __user *buffer, size_t *lenp, loff_t *ppos)
>  {
> +	int ret;
>  	struct ctl_table ipc_table;
>  
>  	memcpy(&ipc_table, table, sizeof(ipc_table));
>  	ipc_table.data = get_ipc(table);
>  
> -	return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
> +	ret = proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
> +
> +	table->flags |= ipc_table.flags; /* Copy back any change in flags */

This seems fragile, why are we requiring this to be done by the users of
CTL_FLAGS_CLAMP_RANGE ?

  Luis