From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751585AbdF1LM7 (ORCPT ); Wed, 28 Jun 2017 07:12:59 -0400 Received: from mail-oi0-f52.google.com ([209.85.218.52]:33084 "EHLO mail-oi0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500AbdF1LMx (ORCPT ); Wed, 28 Jun 2017 07:12:53 -0400 MIME-Version: 1.0 In-Reply-To: References: <85d51d3551b676ba1fc40e8fbddd2eadd056d8dd.1498140838.git.dvyukov@google.com> <20170628100246.7nsvhblgi3xjbc4m@breakpoint.cc> From: Dmitry Vyukov Date: Wed, 28 Jun 2017 13:12:31 +0200 Message-ID: Subject: Re: [PATCH] locking/atomics: don't alias ____ptr To: Thomas Gleixner Cc: Sebastian Andrzej Siewior , Ingo Molnar , Mark Rutland , Peter Zijlstra , Will Deacon , "H. Peter Anvin" , Andrey Ryabinin , kasan-dev , "x86@kernel.org" , LKML , Andrew Morton , "linux-mm@kvack.org" , Linus Torvalds Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Dmitry Vyukov wrote: >> On Wed, Jun 28, 2017 at 12:02 PM, Sebastian Andrzej Siewior wrote: >> > @@ -359,16 +359,16 @@ static __always_inline bool atomic64_add_negative(s64 i, atomic64_t *v) >> > >> > #define cmpxchg64(ptr, old, new) \ >> > ({ \ >> > - __typeof__(ptr) ____ptr = (ptr); \ >> > - kasan_check_write(____ptr, sizeof(*____ptr)); \ >> > - arch_cmpxchg64(____ptr, (old), (new)); \ >> > + __typeof__(ptr) ____ptr64 = (ptr); \ >> > + kasan_check_write(____ptr64, sizeof(*____ptr64));\ >> > + arch_cmpxchg64(____ptr64, (old), (new)); \ >> > }) >> > >> > #define cmpxchg64_local(ptr, old, new) \ >> > ({ \ >> > - __typeof__(ptr) ____ptr = (ptr); \ >> > - kasan_check_write(____ptr, sizeof(*____ptr)); \ >> > - arch_cmpxchg64_local(____ptr, (old), (new)); \ >> > + __typeof__(ptr) ____ptr64 = (ptr); \ >> > + kasan_check_write(____ptr64, sizeof(*____ptr64));\ >> > + arch_cmpxchg64_local(____ptr64, (old), (new)); \ >> > }) >> > >> > #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ >> >> >> Doh! Thanks for fixing this. I think I've a similar crash in a >> different place when I developed the patch. >> The problem is that when we do: >> >> __typeof__(ptr) ____ptr = (ptr); \ >> arch_cmpxchg64_local(____ptr, (old), (new)); \ >> >> We don't necessary pass value of our just declared ____ptr to >> arch_cmpxchg64_local(). We just pass a symbolic identifier. So if >> arch_cmpxchg64_local() declares own ____ptr and then tries to use what >> we passed ("____ptr") it will actually refer to own variable declared >> rather than to what we wanted to pass in. >> >> In my case I ended up with something like: >> >> __typeof__(foo) __ptr = __ptr; >> >> which compiler decided to turn into 0. >> >> Thank you, macros. >> >> We can add more underscores, but the problem can happen again. Should >> we prefix current function/macro name to all local vars?.. > > Actually we can void that ___ptr dance completely. > > Thanks, > > tglx > > 8<-------------------- > > --- a/include/asm-generic/atomic-instrumented.h > +++ b/include/asm-generic/atomic-instrumented.h > @@ -359,37 +359,32 @@ static __always_inline bool atomic64_add > > #define cmpxchg(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ___ptr = (ptr); \ > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > arch_cmpxchg((ptr), (old), (new)); \ > }) > > #define sync_cmpxchg(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ___ptr = (ptr); \ > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > - arch_sync_cmpxchg(___ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_sync_cmpxchg((ptr), (old), (new)); \ > }) > > #define cmpxchg_local(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg_local(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg_local((ptr), (old), (new)); \ /\/\/\/\/\/\/\/\/\/\/\/\ These are macros. If ptr is foo(), then we will call foo() twice. > }) > > #define cmpxchg64(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg64(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg64((ptr), (old), (new)); \ > }) > > #define cmpxchg64_local(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg64_local(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg64_local((ptr), (old), (new)); \ > }) > > /* > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 7E9166B02C3 for ; Wed, 28 Jun 2017 07:12:53 -0400 (EDT) Received: by mail-oi0-f69.google.com with SMTP id q184so19308360oih.5 for ; Wed, 28 Jun 2017 04:12:53 -0700 (PDT) Received: from mail-oi0-x231.google.com (mail-oi0-x231.google.com. [2607:f8b0:4003:c06::231]) by mx.google.com with ESMTPS id u187si1182227oie.76.2017.06.28.04.12.52 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Jun 2017 04:12:52 -0700 (PDT) Received: by mail-oi0-x231.google.com with SMTP id p187so38651411oif.3 for ; Wed, 28 Jun 2017 04:12:52 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <85d51d3551b676ba1fc40e8fbddd2eadd056d8dd.1498140838.git.dvyukov@google.com> <20170628100246.7nsvhblgi3xjbc4m@breakpoint.cc> From: Dmitry Vyukov Date: Wed, 28 Jun 2017 13:12:31 +0200 Message-ID: Subject: Re: [PATCH] locking/atomics: don't alias ____ptr Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: Sebastian Andrzej Siewior , Ingo Molnar , Mark Rutland , Peter Zijlstra , Will Deacon , "H. Peter Anvin" , Andrey Ryabinin , kasan-dev , "x86@kernel.org" , LKML , Andrew Morton , "linux-mm@kvack.org" , Linus Torvalds On Wed, Jun 28, 2017 at 1:10 PM, Thomas Gleixner wrote: > On Wed, 28 Jun 2017, Dmitry Vyukov wrote: >> On Wed, Jun 28, 2017 at 12:02 PM, Sebastian Andrzej Siewior wrote: >> > @@ -359,16 +359,16 @@ static __always_inline bool atomic64_add_negative(s64 i, atomic64_t *v) >> > >> > #define cmpxchg64(ptr, old, new) \ >> > ({ \ >> > - __typeof__(ptr) ____ptr = (ptr); \ >> > - kasan_check_write(____ptr, sizeof(*____ptr)); \ >> > - arch_cmpxchg64(____ptr, (old), (new)); \ >> > + __typeof__(ptr) ____ptr64 = (ptr); \ >> > + kasan_check_write(____ptr64, sizeof(*____ptr64));\ >> > + arch_cmpxchg64(____ptr64, (old), (new)); \ >> > }) >> > >> > #define cmpxchg64_local(ptr, old, new) \ >> > ({ \ >> > - __typeof__(ptr) ____ptr = (ptr); \ >> > - kasan_check_write(____ptr, sizeof(*____ptr)); \ >> > - arch_cmpxchg64_local(____ptr, (old), (new)); \ >> > + __typeof__(ptr) ____ptr64 = (ptr); \ >> > + kasan_check_write(____ptr64, sizeof(*____ptr64));\ >> > + arch_cmpxchg64_local(____ptr64, (old), (new)); \ >> > }) >> > >> > #define cmpxchg_double(p1, p2, o1, o2, n1, n2) \ >> >> >> Doh! Thanks for fixing this. I think I've a similar crash in a >> different place when I developed the patch. >> The problem is that when we do: >> >> __typeof__(ptr) ____ptr = (ptr); \ >> arch_cmpxchg64_local(____ptr, (old), (new)); \ >> >> We don't necessary pass value of our just declared ____ptr to >> arch_cmpxchg64_local(). We just pass a symbolic identifier. So if >> arch_cmpxchg64_local() declares own ____ptr and then tries to use what >> we passed ("____ptr") it will actually refer to own variable declared >> rather than to what we wanted to pass in. >> >> In my case I ended up with something like: >> >> __typeof__(foo) __ptr = __ptr; >> >> which compiler decided to turn into 0. >> >> Thank you, macros. >> >> We can add more underscores, but the problem can happen again. Should >> we prefix current function/macro name to all local vars?.. > > Actually we can void that ___ptr dance completely. > > Thanks, > > tglx > > 8<-------------------- > > --- a/include/asm-generic/atomic-instrumented.h > +++ b/include/asm-generic/atomic-instrumented.h > @@ -359,37 +359,32 @@ static __always_inline bool atomic64_add > > #define cmpxchg(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ___ptr = (ptr); \ > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > arch_cmpxchg((ptr), (old), (new)); \ > }) > > #define sync_cmpxchg(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ___ptr = (ptr); \ > - kasan_check_write(___ptr, sizeof(*___ptr)); \ > - arch_sync_cmpxchg(___ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_sync_cmpxchg((ptr), (old), (new)); \ > }) > > #define cmpxchg_local(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg_local(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg_local((ptr), (old), (new)); \ /\/\/\/\/\/\/\/\/\/\/\/\ These are macros. If ptr is foo(), then we will call foo() twice. > }) > > #define cmpxchg64(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg64(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg64((ptr), (old), (new)); \ > }) > > #define cmpxchg64_local(ptr, old, new) \ > ({ \ > - __typeof__(ptr) ____ptr = (ptr); \ > - kasan_check_write(____ptr, sizeof(*____ptr)); \ > - arch_cmpxchg64_local(____ptr, (old), (new)); \ > + kasan_check_write((ptr), sizeof(*(ptr))); \ > + arch_cmpxchg64_local((ptr), (old), (new)); \ > }) > > /* > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org