From: Suren Baghdasaryan <surenb@google.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Eric Biggers <ebiggers@kernel.org>, Tejun Heo <tj@kernel.org>,
Zefan Li <lizefan.x@bytedance.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Benjamin Segall <bsegall@google.com>,
Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
cgroups mailinglist <cgroups@vger.kernel.org>,
stable <stable@vger.kernel.org>,
kernel-team <kernel-team@android.com>,
syzbot <syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com>
Subject: Re: [PATCH v3 1/1] psi: Fix uaf issue when psi trigger is destroyed while being polled
Date: Wed, 12 Jan 2022 09:43:43 -0800 [thread overview]
Message-ID: <CAJuCfpGHLXDvMU1GLMcgK_K72_ErPhbcFh1ZvEeHg025yinNuw@mail.gmail.com> (raw)
In-Reply-To: <Yd7oPlxCpnzNmFzc@cmpxchg.org>
)
On Wed, Jan 12, 2022 at 6:40 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Tue, Jan 11, 2022 at 03:23:09PM -0800, Suren Baghdasaryan wrote:
> > With write operation on psi files replacing old trigger with a new one,
> > the lifetime of its waitqueue is totally arbitrary. Overwriting an
> > existing trigger causes its waitqueue to be freed and pending poll()
> > will stumble on trigger->event_wait which was destroyed.
> > Fix this by disallowing to redefine an existing psi trigger. If a write
> > operation is used on a file descriptor with an already existing psi
> > trigger, the operation will fail with EBUSY error.
> > Also bypass a check for psi_disabled in the psi_trigger_destroy as the
> > flag can be flipped after the trigger is created, leading to a memory
> > leak.
> >
> > Fixes: 0e94682b73bf ("psi: introduce psi monitor")
> > Cc: stable@vger.kernel.org
> > Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com
> > Analyzed-by: Eric Biggers <ebiggers@kernel.org>
> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Hmm. kernel test robot notified me of new (which are not really new)
warnings but I don't think this patch specifically introduced them:
kernel/sched/psi.c:1112:21: warning: no previous prototype for
function 'psi_trigger_create' [-Wmissing-prototypes]
struct psi_trigger *psi_trigger_create(struct psi_group *group,
^
kernel/sched/psi.c:1112:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
struct psi_trigger *psi_trigger_create(struct psi_group *group,
^
static
>> kernel/sched/psi.c:1182:6: warning: no previous prototype for function 'psi_trigger_destroy' [-Wmissing-prototypes]
void psi_trigger_destroy(struct psi_trigger *t)
^
kernel/sched/psi.c:1182:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
void psi_trigger_destroy(struct psi_trigger *t)
^
static
kernel/sched/psi.c:1249:10: warning: no previous prototype for
function 'psi_trigger_poll' [-Wmissing-prototypes]
__poll_t psi_trigger_poll(void **trigger_ptr,
^
kernel/sched/psi.c:1249:1: note: declare 'static' if the function
is not intended to be used outside of this translation unit
__poll_t psi_trigger_poll(void **trigger_ptr,
^
This happens with the following config:
CONFIG_CGROUPS=n
CONFIG_PSI=y
With cgroups disabled these functions are defined as non-static but
are not defined in the header
(https://elixir.bootlin.com/linux/latest/source/include/linux/psi.h#L28)
since the only external user cgroup.c is disabled. The cleanest way to
fix these I think is by doing smth like this in psi.c:
struct psi_trigger *_psi_trigger_create(struct psi_group *group, char
*buf, size_t nbytes, enum psi_res res)
{
// original psi_trigger_create code
}
#ifdef CONFIG_CGROUPS
struct psi_trigger *psi_trigger_create(struct psi_group *group, char
*buf, size_t nbytes, enum psi_res res)
{
return _psi_trigger_create(group, buf, nbytes, res);
}
#else
static struct psi_trigger *psi_trigger_create(struct psi_group *group,
char *buf, size_t nbytes, enum psi_res res)
{
return _psi_trigger_create(group, buf, nbytes, res);
}
#endif
Two questions:
1. Is this even worth fixing?
2. If so, I would like to do that as a separate patch (these warnings
are unrelated to the changes in this patch). Would that be ok?
Thanks,
Suren.
next prev parent reply other threads:[~2022-01-12 17:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-11 23:23 [PATCH v3 1/1] psi: Fix uaf issue when psi trigger is destroyed while being polled Suren Baghdasaryan
2022-01-12 6:46 ` Eric Biggers
2022-01-12 10:03 ` Peter Zijlstra
2022-01-12 18:03 ` Linus Torvalds
2022-01-12 14:39 ` Johannes Weiner
2022-01-12 17:43 ` Suren Baghdasaryan [this message]
2022-01-12 17:49 ` Suren Baghdasaryan
2022-01-12 18:16 ` Matthew Wilcox
2022-01-12 18:26 ` Suren Baghdasaryan
2022-01-12 18:44 ` Eric Biggers
2022-01-12 18:53 ` Suren Baghdasaryan
2022-01-12 19:04 ` Eric Biggers
2022-01-12 19:06 ` Suren Baghdasaryan
2022-01-12 19:49 ` Suren Baghdasaryan
2022-01-18 11:18 ` [tip: sched/urgent] " tip-bot2 for Suren Baghdasaryan
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