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Date:   Thu, 12 Sep 2019 18:51:11 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Eugene Syromiatnikov <esyr@redhat.com>
Cc:     linux-kernel@vger.kernel.org,
        Christian Brauner <christian@brauner.io>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH v3] fork: check exit_signal passed in clone3() call
Message-ID: <20190912165110.GA719@redhat.com>
References: <cover.1568223594.git.esyr@redhat.com>
 <4b38fa4ce420b119a4c6345f42fe3cec2de9b0b5.1568223594.git.esyr@redhat.com>
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On 09/11, Eugene Syromiatnikov wrote:
>
> @@ -2562,6 +2564,15 @@ noinline static int copy_clone_args_from_user(struct kernel_clone_args *kargs,
>  	if (copy_from_user(&args, uargs, size))
>  		return -EFAULT;
>  
> +	/*
> +	 * Two separate checks are needed, as valid_signal() takes unsigned long
> +	 * as an argument, and struct kernel_clone_args uses int type
> +	 * for the exit_signal field.
> +	 */
> +	if (unlikely((args.exit_signal > UINT_MAX) ||
> +		     !valid_signal(args.exit_signal)))
> +		return -EINVAL;

OK, I equally agree with this version. Although I'd simply do

	if (args.exit_signal > _NSIG)
		return -EINVAL;

but this is cosmetic.

Acked-by: Oleg Nesterov <oleg@redhat.com>