From: Alexey Gladkov <gladkov.alexey@gmail.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
io-uring <io-uring@vger.kernel.org>,
Kernel Hardening <kernel-hardening@lists.openwall.com>,
Linux Containers <containers@lists.linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <christian.brauner@ubuntu.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
Kees Cook <keescook@chromium.org>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting
Date: Mon, 18 Jan 2021 20:45:51 +0100 [thread overview]
Message-ID: <20210118194551.h2hrwof7b3q5vgoi@example.org> (raw)
In-Reply-To: <CAHk-=wjsg0Lgf1Mh2UiJE4sqBDDo0VhFVBUbhed47ot2CQQwfQ@mail.gmail.com>
On Mon, Jan 18, 2021 at 11:14:48AM -0800, Linus Torvalds wrote:
> On Fri, Jan 15, 2021 at 6:59 AM Alexey Gladkov <gladkov.alexey@gmail.com> wrote:
> >
> > @@ -152,10 +153,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid)
> > ucounts = new;
> > }
> > }
> > - if (ucounts->count == INT_MAX)
> > - ucounts = NULL;
> > - else
> > - ucounts->count += 1;
> > + refcount_inc(&ucounts->count);
> > spin_unlock_irq(&ucounts_lock);
> > return ucounts;
> > }
>
> This is wrong.
>
> It used to return NULL when the count saturated.
>
> Now it just silently saturates.
>
> I'm not sure how many people care, but that NULL return ends up being
> returned quite widely (through "inc_uncount()" and friends).
>
> The fact that this has no commit message at all to explain what it is
> doing and why is also a grounds for just NAK.
Sorry about that. I thought that this code is not needed when switching
from int to refcount_t. I was wrong. I'll think about how best to check
it.
--
Rgrds, legion
next prev parent reply other threads:[~2021-01-18 19:47 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 14:57 [RFC PATCH v3 0/8] Count rlimits in each user namespace Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting Alexey Gladkov
2021-01-18 19:14 ` Linus Torvalds
2021-01-18 19:45 ` Alexey Gladkov [this message]
2021-01-18 20:34 ` Linus Torvalds
2021-01-18 20:56 ` Alexey Gladkov
2021-01-19 4:35 ` Kaiwan N Billimoria
2021-01-20 1:57 ` Eric W. Biederman
2021-01-20 1:58 ` Eric W. Biederman
2021-01-21 12:04 ` Alexey Gladkov
2021-01-21 15:50 ` Eric W. Biederman
2021-01-21 16:07 ` Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 2/8] Add a reference to ucounts for each cred Alexey Gladkov
2021-01-18 8:31 ` [PATCH v4 " Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 3/8] Move RLIMIT_NPROC counter to ucounts Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 4/8] Move RLIMIT_MSGQUEUE " Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 5/8] Move RLIMIT_SIGPENDING " Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 6/8] Move RLIMIT_MEMLOCK " Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 7/8] Move RLIMIT_NPROC check to the place where we increment the counter Alexey Gladkov
2021-01-15 14:57 ` [RFC PATCH v3 8/8] kselftests: Add test to check for rlimit changes in different user namespaces Alexey Gladkov
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