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From: Alexey Gladkov <legion@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Containers <containers@lists.linux.dev>
Subject: Re: [GIT PULL] ucounts: Count rlimits in each user namespace
Date: Tue, 29 Jun 2021 19:17:57 +0200	[thread overview]
Message-ID: <20210629171757.shyr222zjpm6ev5t@example.org> (raw)
In-Reply-To: <CAHk-=wj1z-NKxedgZvSS37iH=EKE47PkL=+BYccAUtsuB1sySQ@mail.gmail.com>

On Mon, Jun 28, 2021 at 08:47:12PM -0700, Linus Torvalds wrote:
> On Mon, Jun 28, 2021 at 3:35 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> >
> > This is the work mainly by Alexey Gladkov to limit rlimits to the
> > rlimits of the user that created a user namespace, and to allow users to
> > have stricter limits on the resources created within a user namespace.
> 
> I guess all the performance issues got sorted, since I haven't seen
> any reports from the test robots.
> 
> I do end up with two questions, mainly because of looking at the
> result of the conflict resolution.
> 
> In particular, in __sigqueue_alloc(), two oddities..
> 
> Why the "sigpending < LONG_MAX" test in that
> 
>         if (override_rlimit || (sigpending < LONG_MAX && sigpending <=
> task_rlimit(t, RLIMIT_SIGPENDING))) {
> 
> thing?

inc_rlimit_ucounts() returns long and uses LONG_MAX as an overflow flag.
At the same time, we have increased the size of sigpending from int to
long.

> And why test for "ucounts" being non-NULL in
> 
>                 if (ucounts && dec_rlimit_ucounts(ucounts,
> UCOUNT_RLIMIT_SIGPENDING, 1))
>                         put_ucounts(ucounts);
> 
> when afaik both of those should be happy with a NULL 'ucounts' pointer
> (if it was NULL, we certainly already used it for the reverse
> operations for get_ucounts() and inc_rlimit_ucounts()..)

The get_ucount() can theoretically return NULL. It increments the
reference counter and if it overflows, the function will return NULL.

> Hmm?
> 
> And somebody should verify that I didn't screw anything up in my merge
> resolution. It all looked very straightforward, but mistakes happen..

-- 
Rgrds, legion


  parent reply	other threads:[~2021-06-29 17:18 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-28 22:35 Eric W. Biederman
2021-06-29  3:47 ` Linus Torvalds
2021-06-29 15:04   ` Eric W. Biederman
2021-06-29 15:51   ` Eric W. Biederman
2021-06-29 16:34     ` Linus Torvalds
2021-06-29 16:42       ` Eric W. Biederman
2021-06-29 17:09         ` Eric W. Biederman
2021-07-01 16:41           ` Alexey Gladkov
2021-07-01 20:05             ` Eric W. Biederman
2021-06-29 17:17   ` Alexey Gladkov [this message]
2021-06-29 18:07     ` Linus Torvalds
2021-06-29 20:20       ` Alexey Gladkov
2021-06-29 20:33         ` Linus Torvalds
2021-06-29 21:22           ` Alexey Gladkov
2021-07-02 17:54           ` [PATCH] ucounts: Fix UCOUNT_RLIMIT_SIGPENDING counter leak Alexey Gladkov
2021-07-02 22:13             ` Linus Torvalds
2021-07-07 16:50               ` Alexey Gladkov
2021-07-07 17:23                 ` Linus Torvalds
2021-07-08 10:33                   ` [PATCH v2] " Alexey Gladkov
2021-07-08 18:44                     ` Linus Torvalds
2021-07-08 11:00                   ` [PATCH] ucounts: " Alexey Gladkov
2021-06-29  3:50 ` [GIT PULL] ucounts: Count rlimits in each user namespace pr-tracker-bot

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