From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.skhynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 9FF5C347DD for ; Fri, 11 Jul 2025 02:09:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=166.125.252.92 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752199750; cv=none; b=Qx0LKZjLQqvha3G+LAHLEIl38RnHIB4u4CWgSgpH7mCd+9t3mKoNNm6GcBpxRaJujJiMrHMLZjUsvShB3m1E9aod2yIOIkv01/eJsavmJ0RyWXnD3K24sK4oIFmy0NT8mICLLmDTN4ncwgL88T43esAL9lyvd8s9A56W3q8zf4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752199750; c=relaxed/simple; bh=zqq57u2WVfgXoEdamVTbfR05Ve7afEYjp1upTRr2SY0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KkBplkQVlJ92shI7UbWcYcGFNAvVQp16n/CfzxcYGsIEoE7maLbg+8FuwQj0UxoGh82AOlTOZt8Tr1u7GjHrKCvHRaCPgFJa30OEMKDqAKueRtyKqMDM2ngeOKv4OGKMORtUMfrfNG9JbpjuT84ssC1OAEoLiSQomj+V5mR0DXM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com; spf=pass smtp.mailfrom=sk.com; arc=none smtp.client-ip=166.125.252.92 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=sk.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sk.com X-AuditID: a67dfc5b-669ff7000002311f-28-6870723f8102 Date: Fri, 11 Jul 2025 11:08:58 +0900 From: Byungchul Park To: Andrey Konovalov Cc: Yeoreum Yun , akpm@linux-foundation.org, glider@google.com, dvyukov@google.com, vincenzo.frascino@arm.com, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, max.byungchul.park@gmail.com, ysk@kzalloc.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, kernel_team@skhynix.com Subject: Re: [PATCH v2] kasan: remove kasan_find_vm_area() to prevent possible deadlock Message-ID: <20250711020858.GA78977@system.software.com> References: <20250703181018.580833-1-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrJIsWRmVeSWpSXmKPExsXC9ZZnoa59UUGGwex1IhZz1q9hs/g+cTq7 xbSLk5gtlj35x2Qx4WEbu0X7x73MFiue3WeyuLxrDpvFvTX/WS0urb7AYnFhYi+rxb6OB0wW e//9ZLGY+8XQ4svqVWwO/B5r5q1h9Ng56y67R8u+W+weCzaVeuyZeJLNY9OqTiDxaRK7x8Lf L5g93p07x+5xYsZvFo8Xm2cyenzeJBfAE8Vlk5Kak1mWWqRvl8CVcb9hIWPBV8GKi02bWRsY d/J0MXJySAiYSJx4e4YFxv7eeRfMZhFQlXh94Dg7iM0moC5x48ZPZhBbREBbYsKNX0A1XBzM Am3MEn8232UFSQgLREo0b7vGBGLzClhIfFswGaxISKCBUWL+m14WiISgxMmZT8BsZqCpf+Zd AprKAWRLSyz/xwERlpdo3jobbBmnQKBE+7Z/YLaogLLEgW3HmUBmSgisYpe4u3wOO8TVkhIH V9xgmcAoOAvJillIVsxCWDELyYoFjCyrGIUy88pyEzNzTPQyKvMyK/SS83M3MQIjdFntn+gd jJ8uBB9iFOBgVOLhdVidnyHEmlhWXJl7iFGCg1lJhHedb0GGEG9KYmVValF+fFFpTmrxIUZp DhYlcV6jb+UpQgLpiSWp2ampBalFMFkmDk6pBka3E29YplfUyb5eGuf+8Mmavt1Ct10TdvX4 SdeIFi8X62bovjZl9nWNUxpxd4IuFLzRWqn/eZJjxvobVgIbtf8J7fj//K+szN48hogXhnfb Xfjbvkhv/qfIWL9XdofBvUVcDzd1ld+uiBLqd8p9o/r0Z8G8H/ebawp2zbjgFbDa5rD/WrXs /QeUWIozEg21mIuKEwEDMfAizAIAAA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrAIsWRmVeSWpSXmKPExsXC5WfdrGtfVJBhcGEqi8Wc9WvYLL5PnM5u Me3iJGaLZU/+MVlMeNjGbtH+cS+zxYpn95ksDs89yWpxedccNot7a/6zWlxafYHF4sLEXlaL fR0PmCz2/vvJYjH3i6HFl9Wr2BwEPNbMW8PosXPWXXaPln232D0WbCr12DPxJJvHplWdQOLT JHaPhb9fMHu8O3eO3ePEjN8sHi82z2T0WPziA5PH501yAbxRXDYpqTmZZalF+nYJXBn3GxYy FnwVrLjYtJm1gXEnTxcjJ4eEgInE9867LCA2i4CqxOsDx9lBbDYBdYkbN34yg9giAtoSE278 Aqrh4mAWaGOW+LP5LitIQlggUqJ52zUmEJtXwELi24LJYEVCAg2MEvPf9LJAJAQlTs58AmYz A039M+8S0FQOIFtaYvk/DoiwvETz1tlgyzgFAiXat/0Ds0UFlCUObDvONIGRbxaSSbOQTJqF MGkWkkkLGFlWMYpk5pXlJmbmmOoVZ2dU5mVW6CXn525iBMbbsto/E3cwfrnsfohRgINRiYfX YXV+hhBrYllxZe4hRgkOZiUR3nW+BRlCvCmJlVWpRfnxRaU5qcWHGKU5WJTEeb3CUxOEBNIT S1KzU1MLUotgskwcnFINjAkZwV9fGeso6bmLPPGKMfWun/37ye1FN13mnrl5jOui5qKFl0/V PP3N1ZaV+vipSbKxp/3dZ7f2fE77c+v3yWOXdi0IUlwzoSuvoJlpzYQcebbJb6/euCn/ZqvD ZIMvzhNuFG78Z188p+1gpeoOcYal3BrLL2y9oNNV+OC95gLP8xvn3OZ4kTpfiaU4I9FQi7mo OBEAuCK4YLMCAAA= X-CFilter-Loop: Reflected On Thu, Jul 10, 2025 at 02:43:15PM +0200, Andrey Konovalov wrote: > On Thu, Jul 3, 2025 at 8:10 PM Yeoreum Yun wrote: > > > > find_vm_area() couldn't be called in atomic_context. > > If find_vm_area() is called to reports vm area information, > > kasan can trigger deadlock like: > > > > CPU0 CPU1 > > vmalloc(); > > alloc_vmap_area(); > > spin_lock(&vn->busy.lock) > > spin_lock_bh(&some_lock); > > > > > > spin_lock(&some_lock); > > > > kasan_report(); > > print_report(); > > print_address_description(); > > kasan_find_vm_area(); > > find_vm_area(); > > spin_lock(&vn->busy.lock) // deadlock! > > > > To prevent possible deadlock while kasan reports, remove kasan_find_vm_area(). > > > > Fixes: c056a364e954 ("kasan: print virtual mapping info in reports") > > Reported-by: Yunseong Kim > > Signed-off-by: Yeoreum Yun > > As a fix: > > Acked-by: Andrey Konovalov > > But it would be great to figure out a way to eventually restore this > functionality; I'll file a bug for this once this patch lands. The > virtual mapping info helps with real issues: e.g. just recently it > helped me to quickly see the issue that caused a false-positive report 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? If it's unacceptable for some reasons, why don't we introduce kind of try_find_vm_area() using trylock so as to go ahead only if there's no lock contention? Byungchul > [1]. > > [1] https://lore.kernel.org/all/CA+fCnZfzHOFjVo43UZK8H6h3j=OHjfF13oFJvT0P-SM84Oc4qQ@mail.gmail.com/