linux-kernel - Re: [PATCH] sysctl: add bound to panic

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Message-ID: <20200710112803.GI12769@casper.infradead.org>
Date:   Fri, 10 Jul 2020 12:28:03 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Changming Liu <charley.ashbringer@...il.com>,
        keescook@...omium.org, mcgrof@...nel.org, yzaikin@...gle.com,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] sysctl: add bound to panic_timeout to prevent overflow

On Thu, Jul 09, 2020 at 08:31:39PM -0700, Randy Dunlap wrote:
> > +/* this is needed for setting boundery for panic_timeout to prevent it from overflow*/
> 
>                                  boundary (or max value)                       overflow */
> 
> > +static int panic_time_max = INT_MAX / 1000;

Or just simplify the comment.

/* Prevent overflow in panic() */

Or perhaps better, fix panic() to not overflow.

-		for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
+		for (i = 0; i / 1000 < panic_timeout; i += PANIC_TIMER_STEP) {

you probably also want to change i to be a long long or the loop may never
terminate.