linux-kernel - Re: [PATCH] sysctl: fix proc_doulongvec_ms_jiffies

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Message-ID: <CA+55aFw4FgM4xf2zq7z0UbR89GQnhyLERv0=42_v0=wkPz7q3Q@mail.gmail.com>
Date:   Thu, 26 Jan 2017 09:25:08 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sysctl: fix proc_doulongvec_ms_jiffies_minmax()

On Wed, Jan 25, 2017 at 6:20 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>
> We perform the conversion between kernel jiffies and ms only
> when exporting kernel value to user space.
>
> We need to do the opposite operation when value is written
> by user.

Applied. The interface is really confusing - I had to check whether
the min/max values were in jiffies or in ms, but it looks right. It
would probably be good to verify any overflow conditions, but we do
check the min/max after the conversion, so overflows are at least only
an inconvenience, not a "you can set invalid values".

The one overflow case I can imagine is trying to set some unlimited
value, and now due to the conversion math it's not unlimited any more,
and it just happened to work.

But the current code is clearly wrong. Of course, something might end
up depending on it being wrong, so..

           Linus