linux-kernel - Re: [PATCH v2] signal: Avoid undefined behaviour in kill_something

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Message-ID: <20170605130903.GP9248@dhcp22.suse.cz>
Date:   Mon, 5 Jun 2017 15:09:03 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     zhongjiang <zhongjiang@...wei.com>
Cc:     akpm@...ux-foundation.org, oleg@...hat.com, vbabka@...e.cz,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        qiuxishi@...wei.com
Subject: Re: [PATCH v2] signal: Avoid undefined behaviour in
 kill_something_info

On Mon 05-06-17 20:53:27, zhongjiang wrote:
> diff --git a/kernel/signal.c b/kernel/signal.c
> index ca92bcf..63148f7 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1395,6 +1395,12 @@ static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
>  
>  	read_lock(&tasklist_lock);
>  	if (pid != -1) {
> +		/*
> +	 	 * -INT_MIN is undefined, it need to exclude following case to 
> + 		 * avoid the UBSAN detection.
> +		 */
> +		if (pid == INT_MIN)
> +			return -ESRCH;

this will obviously keep the tasklist_lock held...

>  		ret = __kill_pgrp_info(sig, info,
>  				pid ? find_vpid(-pid) : task_pgrp(current));
>  	} else {
> -- 
> 1.7.12.4

-- 
Michal Hocko
SUSE Labs