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From: Byungchul Park <byungchul@sk.com>
To: Yeo Reum Yun <YeoReum.Yun@arm.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>,
	"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
	"glider@google.com" <glider@google.com>,
	"dvyukov@google.com" <dvyukov@google.com>,
	Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
	"bigeasy@linutronix.de" <bigeasy@linutronix.de>,
	"clrkwllms@kernel.org" <clrkwllms@kernel.org>,
	"rostedt@goodmis.org" <rostedt@goodmis.org>,
	"max.byungchul.park@gmail.com" <max.byungchul.park@gmail.com>,
	"ysk@kzalloc.com" <ysk@kzalloc.com>,
	"kasan-dev@googlegroups.com" <kasan-dev@googlegroups.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-rt-devel@lists.linux.dev" <linux-rt-devel@lists.linux.dev>,
	"kernel_team@skhynix.com" <kernel_team@skhynix.com>,
	"urezki@gmail.com" <urezki@gmail.com>
Subject: Re: [PATCH v2] kasan: remove kasan_find_vm_area() to prevent possible deadlock
Date: Mon, 14 Jul 2025 08:27:40 +0900	[thread overview]
Message-ID: <20250713232740.GA18327@system.software.com> (raw)
In-Reply-To: <GV1PR08MB1052126BB553BD36DA768C998FB4AA@GV1PR08MB10521.eurprd08.prod.outlook.com>

On Sat, Jul 12, 2025 at 03:46:10PM +0000, Yeo Reum Yun wrote:
> Hi ByungChul,
> 
> [...]
> > I checked the critical section by &vn->busy.lock in find_vm_area().  The
> > time complextity looks O(log N).  I don't think an irq disabled section
> > of O(log N) is harmful.  I still think using
> > spin_lock_irqsave(&vn->busy.lock) can resolve this issue with no worry
> > of significant irq delay.  Am I missing something?
> 
> I don't agree for this.
> since in PREEMPT_RT case, it has the same problem.
> 
> In case of PREEMPT_RT, spin_lock_irqsave() becomes rt_spin_lock() which is sleepable.
> But, KASAN calls "rt_spin_lock()" holding raw_spin_lock_irqsave() which is definitely wrong.

It's another issue than irq handling latency, but it's about lock usage
correctness.  You are right.

	Byungchul

> But as Uladzislau said, without reference count manage, UAF can always happen.
> IOW, If KASAN to dump vm information, I think we need:
>     1. manage reference for vmap_area.
>     2. find_vm_area() with rcu version.
> 
> 
> Thanks.
> 
> --
> Sincerely,
> Yeoreum Yun

  reply	other threads:[~2025-07-13 23:27 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-07-03 18:10 [PATCH v2] kasan: remove kasan_find_vm_area() to prevent possible deadlock Yeoreum Yun
2025-07-03 18:44 ` Andrey Konovalov
2025-07-03 18:55   ` Yeoreum Yun
2025-07-03 19:05     ` Andrey Konovalov
2025-07-03 19:13       ` Yeoreum Yun
2025-07-04 13:07       ` Andrey Ryabinin
2025-07-03 18:57 ` Yeo Reum Yun
2025-07-03 20:35 ` Andrew Morton
2025-07-04 12:40 ` Andrey Ryabinin
2025-07-07  8:30 ` Sebastian Andrzej Siewior
2025-07-07  8:33   ` Yeoreum Yun
2025-07-07  8:44     ` Sebastian Andrzej Siewior
2025-07-07 13:49       ` Yeoreum Yun
2025-07-10 12:43 ` Andrey Konovalov
2025-07-11  2:08   ` Byungchul Park
2025-07-11  2:11     ` Byungchul Park
2025-07-11  8:54       ` Uladzislau Rezki
2025-07-12 15:46       ` Yeo Reum Yun
2025-07-13 23:27         ` Byungchul Park [this message]
2025-07-16  9:09           ` Uladzislau Rezki
2025-07-16 15:28             ` Marco Elver

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