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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 7 Jul 2021 10:23:35 -0700
Message-ID: <CAHk-=wirhF8G1XniAfxzJXCYUnuAx23Q1WLi_n4+HGsUXv72KQ@mail.gmail.com>
Subject: Re: [PATCH] ucounts: Fix UCOUNT_RLIMIT_SIGPENDING counter leak
To:     Alexey Gladkov <legion@kernel.org>
Cc:     "Eric W. Biederman" <ebiederm@xmission.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Containers <containers@lists.linux.dev>
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On Wed, Jul 7, 2021 at 9:50 AM Alexey Gladkov <legion@kernel.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?

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?

              Linus