Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752877AbbBQGpz (ORCPT ); Tue, 17 Feb 2015 01:45:55 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:22746 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751591AbbBQGpw (ORCPT ); Tue, 17 Feb 2015 01:45:52 -0500 Message-ID: <54E2E2CA.8020004@huawei.com> Date: Tue, 17 Feb 2015 14:42:18 +0800 From: Bamvor Jian Zhang User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130509 Thunderbird/17.0.6 MIME-Version: 1.0 To: Catalin Marinas CC: Chris Metcalf , , , , , "dingtianhong@huawei.com" , , "linux-kernel@vger.kernel.org" , Will Deacon , , "lizefan@huawei.com" , , , , , , , , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH] compat: Fix endian issue in union sigval References: <1423563011-12377-1-git-send-email-bamvor.zhangjian@huawei.com> <20150210122718.GC32052@e104818-lin.cambridge.arm.com> <54DB3B60.4050100@huawei.com> <20150211154054.GD9058@e104818-lin.cambridge.arm.com> <54DDAF2B.2070707@huawei.com> <20150213104455.GA3508@e104818-lin.cambridge.arm.com> <54DE730D.3090100@ezchip.com> <20150214112220.GB10246@MBP.local> In-Reply-To: <20150214112220.GB10246@MBP.local> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.75.31] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.54E2E2E6.00D5,ss=1,re=0.001,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: f9a882cddbc9b6c6a6e96df476d0c61c Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3826 Lines: 80 On 2015/2/14 19:22, Catalin Marinas wrote: > On Fri, Feb 13, 2015 at 04:56:29PM -0500, Chris Metcalf wrote: >> On 2/13/2015 5:44 AM, Catalin Marinas wrote: >>> On Fri, Feb 13, 2015 at 04:00:43PM +0800, Bamvor Jian Zhang wrote: >>>> diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c >>>> index e299de396e9b..32601939a3c8 100644 >>>> --- a/arch/arm64/kernel/signal32.c >>>> +++ b/arch/arm64/kernel/signal32.c >>>> @@ -154,8 +154,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from) >>>> case __SI_TIMER: >>>> err |= __put_user(from->si_tid, &to->si_tid); >>>> err |= __put_user(from->si_overrun, &to->si_overrun); >>>> - err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, >>>> - &to->si_ptr); >>>> + err |= __put_user(from->si_int, &to->si_int); >>>> break; >>>> case __SI_POLL: >>>> err |= __put_user(from->si_band, &to->si_band); >>>> @@ -184,7 +183,7 @@ int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from) >>>> case __SI_MESGQ: /* But this is */ >>>> err |= __put_user(from->si_pid, &to->si_pid); >>>> err |= __put_user(from->si_uid, &to->si_uid); >>>> - err |= __put_user((compat_uptr_t)(unsigned long)from->si_ptr, &to->si_ptr); >>>> + err |= __put_user(from->si_int, &to->si_int); >>>> break; >>>> case __SI_SYS: >>>> err |= __put_user((compat_uptr_t)(unsigned long) >> >> I must be confused here, but I don't see that these do anything different. >> >> If we are writing 32 bits to to->si_ptr or to->si_int, either way the high 32 bits >> are irrelevant. So whether we read it from from->si_ptr and massage the high bits, >> or just read it from from->si_int as a straight-up 32-bit quantity, either way it >> seems we should end up writing the same bits to userspace. >> >> I would understand the argument if we were overlaying the si_ptr/si_int union >> from a kernel-side siginfo_t where si_ptr and si_int are different sizes >> onto userspace, but it doesn't seem we ever do that. > > That's the problem, "from" above is a kernel siginfo_t while "to" is a > compat_siginfo_t. The call paths go something like: > > 1. user populates sival_int compat_sigevent and invokes > compat_sys_mq_notify() > 2. kernel get_compat_sigevent() copies compat_sigevent into the native > sigevent. compat and native sival_int are the same, no problem so > far. The other half of 64-bit sival_ptr is zeroed by a memset in this > function (this other half can be top or bottom, depending on > endianness) > 3. signal is about to be delivered to user via arch code. The > compat_ptr(from->si_ptr) conversion always takes the least > significant part of the native si_ptr. On big endian 64-bit, this is > zero because get_compat_sigevent() populated the top part of si_ptr > with si_int. > > So delivering such signals to compat user always sets si_int to 0. > Little endian is fine. > > A similar example is sys_timer_create() which takes a sigevent argument. > Maybe Bamvor has a test case. > A similar example is sys_timer_create() which takes a sigevent argument. > Maybe Bamvor has a test case. Yeap, this issue is came from glibc rt testcases(tst-cputimer1, tst-cputimer2, tst-cputimer3, tst-timer4, tst-timer5). The above test cases include timer_create syscall with sigevent.sigev_notify = SIGEV_THREAD. They failed when they compiled as armeb elf and run on aarch64_be kernel. When I try to fix it, I found sys_mq_notify is similar. regards bamvor > (btw, I'm off for a week, I'll follow up when I get back) > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/