From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from invmail4.hynix.com (exvmail4.hynix.com [166.125.252.92]) by smtp.subspace.kernel.org (Postfix) with ESMTP id D8C12B665 for ; Fri, 11 Jul 2025 02:11:06 +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=1752199870; cv=none; b=gqhRlFrQlcljAL6mntUFmSR6rEKiMWsu4B7ZGBnwOAZiR54rDVDE4HBgZHb0DDqjru1QXYCRgjnDv9C2DCedaDlHt7sbmWkOMdWgRf2xCZI++o1VM4R3tsgtw4Bx4GrYJ6XPm9nohgkoM/V4Xti/Mc8InuaNhdPyh7knO5IPCx4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752199870; c=relaxed/simple; bh=oyqpaHCXNtnH2AyieviUSp/gVpxZ/bNXm0FM0r7skuI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QMbS7Lx1PcqDZfZ8WumkG1pHyEvzzjIROLxlwWZzRm2U2veUY1WInaJP661Dvb6LJ3g44bi45svn7kDLAz49cHxzJWigzQhh+4HqhcYpL+FRbx57AkKWIQ00hUYw6Dopn+LZ1FM92D0cBCtMTBHCAilkM9fhnOBMNu3MeGL+nwE= 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-681ff7000002311f-17-687072b9b6c9 Date: Fri, 11 Jul 2025 11:11:00 +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: <20250711021100.GA4320@system.software.com> References: <20250703181018.580833-1-yeoreum.yun@arm.com> <20250711020858.GA78977@system.software.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: <20250711020858.GA78977@system.software.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrJIsWRmVeSWpSXmKPExsXC9ZZnoe7OooIMg6/fNS3mrF/DZvF94nR2 i2kXJzFbLHvyj8liwsM2dov2j3uZLVY8u89kcXnXHDaLe2v+s1pcWn2BxeLCxF5Wi30dD5gs 9v77yWIx94uhxZfVq9gc+D3WzFvD6LFz1l12j5Z9t9g9Fmwq9dgz8SSbx6ZVnUDi0yR2j4W/ XzB7vDt3jt3jxIzfLB4vNs9k9Pi8SS6AJ4rLJiU1J7MstUjfLoEr4/WUSWwFJ4QrOtYdZG5g 3MfbxcjJISFgInH52RoWGHvz8dvMIDaLgKrE7J/vmEBsNgF1iRs3foLFRQS0JSbc+AVUz8XB LNDGLPFn811WkISwQKRE87ZrYA28AuYSzU9nghUJCaxnlPj16idUQlDi5MwnYNuYgab+mXcJ aCoHkC0tsfwfB0RYXqJ562ywZZwClhKvp2xlB7FFBZQlDmw7zgQyU0JgGbvE8/NLmSGulpQ4 uOIGywRGwVlIVsxCsmIWwopZSFYsYGRZxSiUmVeWm5iZY6KXUZmXWaGXnJ+7iREYoctq/0Tv YPx0IfgQowAHoxIPr8Pq/Awh1sSy4srcQ4wSHMxKIrzrfAsyhHhTEiurUovy44tKc1KLDzFK c7AoifMafStPERJITyxJzU5NLUgtgskycXBKNTBKeBz6yvDh+PZ8DdbUkoN8iw5FzH4Vlc0l MmH219LrNoopYnXpC+6pm1dyr9zLHq7NdvvXhWnSHx9sWr7HY9Lm20uLz++NWDrB47/G+kd3 tmxxPfn01NmFJ126196uC5vzQFa8Sr4jOztZpbnzckZx5or1+q3TK7dOTJx89JmHyrLLlVcz TUPuK7EUZyQaajEXFScCAB4frvrMAgAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrAIsWRmVeSWpSXmKPExsXC5WfdrLuzqCDDoPuktMWc9WvYLL5PnM5u Me3iJGaLZU/+MVlMeNjGbtH+cS+zxYpn95ksDs89yWpxedccNot7a/6zWlxafYHF4sLEXlaL fR0PmCz2/vvJYjH3i6HFl9Wr2BwEPNbMW8PosXPWXXaPln232D0WbCr12DPxJJvHplWdQOLT JHaPhb9fMHu8O3eO3ePEjN8sHi82z2T0WPziA5PH501yAbxRXDYpqTmZZalF+nYJXBmvp0xi KzghXNGx7iBzA+M+3i5GTg4JAROJzcdvM4PYLAKqErN/vmMCsdkE1CVu3PgJFhcR0JaYcOMX SxcjFwezQBuzxJ/Nd1lBEsICkRLN266BNfAKmEs0P50JViQksJ5R4tern1AJQYmTM5+wgNjM QFP/zLsENJUDyJaWWP6PAyIsL9G8dTbYMk4BS4nXU7ayg9iiAsoSB7YdZ5rAyDcLyaRZSCbN Qpg0C8mkBYwsqxhFMvPKchMzc0z1irMzKvMyK/SS83M3MQLjbVntn4k7GL9cdj/EKMDBqMTD 67A6P0OINbGsuDL3EKMEB7OSCO8634IMId6UxMqq1KL8+KLSnNTiQ4zSHCxK4rxe4akJQgLp iSWp2ampBalFMFkmDk6pBsY718TSjfVnFbI07tWb/Jj77yyxzhvpdYqHVRizjy94rv5+l8tJ Ywe9STF39VZLvY8QWVUnaW55LCBWWkY9aYmmgdb0k2F63oz1jNIXefxUWq4tavfuC565/nu+ 9HnvqCkF1iktiwT2+QesrlqjsvbA1Y6WhYt/7KxPO95du4tr87WY2SGy15VYijMSDbWYi4oT AQ9n3/KzAgAA X-CFilter-Loop: Reflected On Fri, Jul 11, 2025 at 11:08:58AM +0900, Byungchul Park wrote: > 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? I prefer this one tho. Byungchul > > 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/