linux-kernel - Re: [PATCH] ucounts: Fix UCOUNT_RLIMIT

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Message-ID: <20210708110016.seeviageyspgctzk@example.org>
Date:   Thu, 8 Jul 2021 13:00:16 +0200
From:   Alexey Gladkov <gladkov.alexey@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Containers <containers@...ts.linux.dev>
Subject: Re: [PATCH] ucounts: Fix UCOUNT_RLIMIT_SIGPENDING counter leak

On Wed, Jul 07, 2021 at 10:23:35AM -0700, Linus Torvalds wrote:
> On Wed, Jul 7, 2021 at 9:50 AM Alexey Gladkov <legion@...nel.org> wrote:
> >
> > >   +             dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_SIGPENDING, 1);
> > >   +             fallthrough;
> > >   +     case LONG_MAX:
> >
> > I think that the counter should be decreased in this case too.
> > inc_rlimit_ucounts() increments the counter in all parent userns. If we
> > don't decrease the counter then the parent userns will have a counter
> > leak.
> 
> Ack. So basically that patch, but move the dec_rlimit_ucounts() into
> the LONG_MAX case?

Yep.

> Would you mind making a real patch with a commit message, and trying
> whatever test-case you had for that KASAN use-after-free report?

Sure. I will.

-- 
Rgrds, legion