From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751839AbbENG3y (ORCPT ); Thu, 14 May 2015 02:29:54 -0400 Received: from mail-pa0-f50.google.com ([209.85.220.50]:35262 "EHLO mail-pa0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750861AbbENG3x (ORCPT ); Thu, 14 May 2015 02:29:53 -0400 Message-ID: <555440D8.3060405@ozlabs.ru> Date: Thu, 14 May 2015 16:29:44 +1000 From: Alexey Kardashevskiy User-Agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: Alex Williamson CC: Gavin Shan , Thomas Huth , Wei Yang , linux-kernel@vger.kernel.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org, David Gibson Subject: Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table() References: <1431358763-24371-1-git-send-email-aik@ozlabs.ru> <1431358763-24371-6-git-send-email-aik@ozlabs.ru> <20150513053337.GA479@gwshan> <5552EF78.6020301@ozlabs.ru> <20150513145136.1a85f536@thh440s> <20150513232745.GA8158@gwshan> <555409B8.3060904@ozlabs.ru> <1431571984.3625.91.camel@redhat.com> In-Reply-To: <1431571984.3625.91.camel@redhat.com> Content-Type: text/plain; charset=koi8-r; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/14/2015 12:53 PM, Alex Williamson wrote: > On Thu, 2015-05-14 at 12:34 +1000, Alexey Kardashevskiy wrote: >> On 05/14/2015 09:27 AM, Gavin Shan wrote: >>> On Wed, May 13, 2015 at 02:51:36PM +0200, Thomas Huth wrote: >>>> On Wed, 13 May 2015 16:30:16 +1000 >>>> Alexey Kardashevskiy wrote: >>>> >>>>> On 05/13/2015 03:33 PM, Gavin Shan wrote: >>>>>> On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote: >>>>>>> At the moment iommu_free_table() only releases memory if >>>>>>> the table was initialized for the platform code use, i.e. it had >>>>>>> it_map initialized (which purpose is to track DMA memory space use). >>>>>>> >>>>>>> With dynamic DMA windows, we will need to be able to release >>>>>>> iommu_table even if it was used for VFIO in which case it_map is NULL >>>>>>> so does the patch. >>>>>>> >>>>>>> Signed-off-by: Alexey Kardashevskiy >>>>>> >>>>>> Reviewed-by: Gavin Shan >>>>>> >>>>>>> --- >>>>>>> arch/powerpc/kernel/iommu.c | 3 +-- >>>>>>> 1 file changed, 1 insertion(+), 2 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c >>>>>>> index 3d47eb3..2c02d4c 100644 >>>>>>> --- a/arch/powerpc/kernel/iommu.c >>>>>>> +++ b/arch/powerpc/kernel/iommu.c >>>>>>> @@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name) >>>>>>> unsigned int order; >>>>>>> >>>>>>> if (!tbl || !tbl->it_map) { >>>>>>> - printk(KERN_ERR "%s: expected TCE map for %s\n", __func__, >>>>>>> - node_name); >>>>>>> + kfree(tbl); >>>>>> >>>>>> I'm not sure if the "tbl" needs to be checked against NULL as kfree() already >>>>>> has the check. But it looks a bit strange to free NULL "tbl" from the code >>>>>> itself. >>>>> >>>>> Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/... >>>>> - they all check the passed pointer for NULL. >>>> >>>> But if tbl is NULL, the tbl->it_map check will fail, won't it? So in >>>> this case, I think you have to keep it. >>>> >>> >>> If I understood your question correctly, "tbl->it_map" won't be checked >>> when "tbl" is NULL because the connection ("||") for the two conditions. >>> The code can be changed to something like below if Alexey want: >>> >>> if (!tbl) >>> return; >>> if (!tbl->itmap) >>> kfree(tbl); >> >> To be precise ;) >> >> if (!tbl->itmap) { >> kfree(tbl); >> return; >> } > > I hope that's not your solution, it clearly segfaults with a null > pointer de-ref if !tbl, which is apparently a concern down this path. I meant the second "if" needs fixing. I need the first one - "if (!tbl)" - anyway. What did I miss? -- Alexey From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id D566B1A03B4 for ; Thu, 14 May 2015 16:29:54 +1000 (AEST) Received: by pabsx10 with SMTP id sx10so74564061pab.3 for ; Wed, 13 May 2015 23:29:52 -0700 (PDT) Message-ID: <555440D8.3060405@ozlabs.ru> Date: Thu, 14 May 2015 16:29:44 +1000 From: Alexey Kardashevskiy MIME-Version: 1.0 To: Alex Williamson Subject: Re: [PATCH kernel v10 05/34] powerpc/iommu: Always release iommu_table in iommu_free_table() References: <1431358763-24371-1-git-send-email-aik@ozlabs.ru> <1431358763-24371-6-git-send-email-aik@ozlabs.ru> <20150513053337.GA479@gwshan> <5552EF78.6020301@ozlabs.ru> <20150513145136.1a85f536@thh440s> <20150513232745.GA8158@gwshan> <555409B8.3060904@ozlabs.ru> <1431571984.3625.91.camel@redhat.com> In-Reply-To: <1431571984.3625.91.camel@redhat.com> Content-Type: text/plain; charset=koi8-r; format=flowed Cc: Thomas Huth , Gavin Shan , linux-kernel@vger.kernel.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org, Wei Yang , David Gibson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/14/2015 12:53 PM, Alex Williamson wrote: > On Thu, 2015-05-14 at 12:34 +1000, Alexey Kardashevskiy wrote: >> On 05/14/2015 09:27 AM, Gavin Shan wrote: >>> On Wed, May 13, 2015 at 02:51:36PM +0200, Thomas Huth wrote: >>>> On Wed, 13 May 2015 16:30:16 +1000 >>>> Alexey Kardashevskiy wrote: >>>> >>>>> On 05/13/2015 03:33 PM, Gavin Shan wrote: >>>>>> On Tue, May 12, 2015 at 01:38:54AM +1000, Alexey Kardashevskiy wrote: >>>>>>> At the moment iommu_free_table() only releases memory if >>>>>>> the table was initialized for the platform code use, i.e. it had >>>>>>> it_map initialized (which purpose is to track DMA memory space use). >>>>>>> >>>>>>> With dynamic DMA windows, we will need to be able to release >>>>>>> iommu_table even if it was used for VFIO in which case it_map is NULL >>>>>>> so does the patch. >>>>>>> >>>>>>> Signed-off-by: Alexey Kardashevskiy >>>>>> >>>>>> Reviewed-by: Gavin Shan >>>>>> >>>>>>> --- >>>>>>> arch/powerpc/kernel/iommu.c | 3 +-- >>>>>>> 1 file changed, 1 insertion(+), 2 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c >>>>>>> index 3d47eb3..2c02d4c 100644 >>>>>>> --- a/arch/powerpc/kernel/iommu.c >>>>>>> +++ b/arch/powerpc/kernel/iommu.c >>>>>>> @@ -714,8 +714,7 @@ void iommu_free_table(struct iommu_table *tbl, const char *node_name) >>>>>>> unsigned int order; >>>>>>> >>>>>>> if (!tbl || !tbl->it_map) { >>>>>>> - printk(KERN_ERR "%s: expected TCE map for %s\n", __func__, >>>>>>> - node_name); >>>>>>> + kfree(tbl); >>>>>> >>>>>> I'm not sure if the "tbl" needs to be checked against NULL as kfree() already >>>>>> has the check. But it looks a bit strange to free NULL "tbl" from the code >>>>>> itself. >>>>> >>>>> Yeah, looks a bit weird, agree, I'll change but in general kfree/vfree/... >>>>> - they all check the passed pointer for NULL. >>>> >>>> But if tbl is NULL, the tbl->it_map check will fail, won't it? So in >>>> this case, I think you have to keep it. >>>> >>> >>> If I understood your question correctly, "tbl->it_map" won't be checked >>> when "tbl" is NULL because the connection ("||") for the two conditions. >>> The code can be changed to something like below if Alexey want: >>> >>> if (!tbl) >>> return; >>> if (!tbl->itmap) >>> kfree(tbl); >> >> To be precise ;) >> >> if (!tbl->itmap) { >> kfree(tbl); >> return; >> } > > I hope that's not your solution, it clearly segfaults with a null > pointer de-ref if !tbl, which is apparently a concern down this path. I meant the second "if" needs fixing. I need the first one - "if (!tbl)" - anyway. What did I miss? -- Alexey