Date: Mon, 18 Jan 2021 20:45:51 +0100 From: Alexey Gladkov <gladkov.alexey@...il.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: LKML <linux-kernel@...r.kernel.org>, io-uring <io-uring@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linux Containers <containers@...ts.linux-foundation.org>, Linux-MM <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <christian.brauner@...ntu.com>, "Eric W . Biederman" <ebiederm@...ssion.com>, Jann Horn <jannh@...gle.com>, Jens Axboe <axboe@...nel.dk>, Kees Cook <keescook@...omium.org>, Oleg Nesterov <oleg@...hat.com> Subject: Re: [RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting 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@...il.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
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