From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-24.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3BD2BC433B4 for ; Tue, 20 Apr 2021 01:33:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C0A5613AE for ; Tue, 20 Apr 2021 01:33:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229514AbhDTBdt (ORCPT ); Mon, 19 Apr 2021 21:33:49 -0400 Received: from linux.microsoft.com ([13.77.154.182]:39766 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229492AbhDTBdt (ORCPT ); Mon, 19 Apr 2021 21:33:49 -0400 Received: from [192.168.0.104] (c-73-42-176-67.hsd1.wa.comcast.net [73.42.176.67]) by linux.microsoft.com (Postfix) with ESMTPSA id 1A67020B8001; Mon, 19 Apr 2021 18:33:18 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 1A67020B8001 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1618882398; bh=JpKoSRIhjAwwrj5WZF4k0/uhpNQqdIHge3YUwLmCw6g=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=JkeWr15eHXH+BqGcoux3YBinokOR9h5F9IETVqdSFBIeEdR7I5TopOqEMzhyW0VYd NBMuute88WTB0RPx1kSYmCMVn08ilR/dfW0/6qGWeqVrmfbh7f3jVArxaLyFTbVwzL qDFx1kZiebGubjtQfEJghUyc4fx8RZ7NhnJLCYxI= Subject: Re: [PATCH] powerpc: Initialize local variable fdt to NULL in elf64_load() To: Michael Ellerman , Daniel Axtens , robh@kernel.org, dan.carpenter@oracle.com Cc: devicetree@vger.kernel.org, linuxppc-dev , kbuild-all@lists.01.org, bauerman@linux.ibm.com, lkp@intel.com References: <20210415191437.20212-1-nramas@linux.microsoft.com> <4edb1433-4d1e-5719-ec9c-fd232b7cf71f@linux.microsoft.com> <87eefag241.fsf@linkitivity.dja.id.au> <87tuo6eh0j.fsf@mpe.ellerman.id.au> <2817d674-d420-580f-a0c1-b842da915a80@linux.microsoft.com> <87pmypdf93.fsf@mpe.ellerman.id.au> From: Lakshmi Ramasubramanian Message-ID: <7f5da2c7-13ff-237c-87ba-a456cbac2bca@linux.microsoft.com> Date: Mon, 19 Apr 2021 18:33:17 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <87pmypdf93.fsf@mpe.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 4/19/21 4:30 PM, Michael Ellerman wrote: > Lakshmi Ramasubramanian writes: >> On 4/16/21 2:05 AM, Michael Ellerman wrote: >> >>> Daniel Axtens writes: >>>>> On 4/15/21 12:14 PM, Lakshmi Ramasubramanian wrote: >>>>> >>>>> Sorry - missed copying device-tree and powerpc mailing lists. >>>>> >>>>>> There are a few "goto out;" statements before the local variable "fdt" >>>>>> is initialized through the call to of_kexec_alloc_and_setup_fdt() in >>>>>> elf64_load(). This will result in an uninitialized "fdt" being passed >>>>>> to kvfree() in this function if there is an error before the call to >>>>>> of_kexec_alloc_and_setup_fdt(). >>>>>> >>>>>> Initialize the local variable "fdt" to NULL. >>>>>> >>>> I'm a huge fan of initialising local variables! But I'm struggling to >>>> find the code path that will lead to an uninit fdt being returned... >>>> >>>> The out label reads in part: >>>> >>>> /* Make kimage_file_post_load_cleanup free the fdt buffer for us. */ >>>> return ret ? ERR_PTR(ret) : fdt; >>>> >>>> As far as I can tell, any time we get a non-zero ret, we're going to >>>> return an error pointer rather than the uninitialised value... >> >> As Dan pointed out, the new code is in linux-next. >> >> I have copied the new one below - the function doesn't return fdt, but >> instead sets it in the arch specific field (please see the link to the >> updated elf_64.c below). >> >> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/tree/arch/powerpc/kexec/elf_64.c?h=for-next >> >>>> >>>> (btw, it does look like we might leak fdt if we have an error after we >>>> successfully kmalloc it.) >>>> >>>> Am I missing something? Can you link to the report for the kernel test >>>> robot or from Dan? >> >> /* >> * Once FDT buffer has been successfully passed to >> kexec_add_buffer(), >> * the FDT buffer address is saved in image->arch.fdt. In that >> case, >> * the memory cannot be freed here in case of any other error. >> */ >> if (ret && !image->arch.fdt) >> kvfree(fdt); >> >> return ret ? ERR_PTR(ret) : NULL; >> >> In case of an error, the memory allocated for fdt is freed unless it has >> already been passed to kexec_add_buffer(). > > It feels like the root of the problem is that the kvfree of fdt is in > the wrong place. It's only allocated later in the function, so the error > path should reflect that. Something like the patch below. > > cheers > > > diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c > index 5a569bb51349..02662e72c53d 100644 > --- a/arch/powerpc/kexec/elf_64.c > +++ b/arch/powerpc/kexec/elf_64.c > @@ -114,7 +114,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, > ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr, > initrd_len, cmdline); > if (ret) > - goto out; > + goto out_free_fdt; > > fdt_pack(fdt); > > @@ -125,7 +125,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, > kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; > ret = kexec_add_buffer(&kbuf); > if (ret) > - goto out; > + goto out_free_fdt; > > /* FDT will be freed in arch_kimage_file_post_load_cleanup */ > image->arch.fdt = fdt; > @@ -140,18 +140,14 @@ static void *elf64_load(struct kimage *image, char *kernel_buf, > if (ret) > pr_err("Error setting up the purgatory.\n"); > > + goto out; > + > +out_free_fdt: > + kvfree(fdt); > out: > kfree(modified_cmdline); > kexec_free_elf_info(&elf_info); > > - /* > - * Once FDT buffer has been successfully passed to kexec_add_buffer(), > - * the FDT buffer address is saved in image->arch.fdt. In that case, > - * the memory cannot be freed here in case of any other error. > - */ > - if (ret && !image->arch.fdt) > - kvfree(fdt); > - > return ret ? ERR_PTR(ret) : NULL; > } > > This looks good to me. Thanks Michael. I'll post the updated patch shortly. -lakshmi From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============2035393431708622482==" MIME-Version: 1.0 From: Lakshmi Ramasubramanian To: kbuild-all@lists.01.org Subject: Re: [PATCH] powerpc: Initialize local variable fdt to NULL in elf64_load() Date: Mon, 19 Apr 2021 18:33:17 -0700 Message-ID: <7f5da2c7-13ff-237c-87ba-a456cbac2bca@linux.microsoft.com> In-Reply-To: <87pmypdf93.fsf@mpe.ellerman.id.au> List-Id: --===============2035393431708622482== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On 4/19/21 4:30 PM, Michael Ellerman wrote: > Lakshmi Ramasubramanian writes: >> On 4/16/21 2:05 AM, Michael Ellerman wrote: >> >>> Daniel Axtens writes: >>>>> On 4/15/21 12:14 PM, Lakshmi Ramasubramanian wrote: >>>>> >>>>> Sorry - missed copying device-tree and powerpc mailing lists. >>>>> >>>>>> There are a few "goto out;" statements before the local variable "fd= t" >>>>>> is initialized through the call to of_kexec_alloc_and_setup_fdt() in >>>>>> elf64_load(). This will result in an uninitialized "fdt" being passed >>>>>> to kvfree() in this function if there is an error before the call to >>>>>> of_kexec_alloc_and_setup_fdt(). >>>>>> >>>>>> Initialize the local variable "fdt" to NULL. >>>>>> >>>> I'm a huge fan of initialising local variables! But I'm struggling to >>>> find the code path that will lead to an uninit fdt being returned... >>>> >>>> The out label reads in part: >>>> >>>> /* Make kimage_file_post_load_cleanup free the fdt buffer for us. */ >>>> return ret ? ERR_PTR(ret) : fdt; >>>> >>>> As far as I can tell, any time we get a non-zero ret, we're going to >>>> return an error pointer rather than the uninitialised value... >> >> As Dan pointed out, the new code is in linux-next. >> >> I have copied the new one below - the function doesn't return fdt, but >> instead sets it in the arch specific field (please see the link to the >> updated elf_64.c below). >> >> https://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git/tree/arch= /powerpc/kexec/elf_64.c?h=3Dfor-next >> >>>> >>>> (btw, it does look like we might leak fdt if we have an error after we >>>> successfully kmalloc it.) >>>> >>>> Am I missing something? Can you link to the report for the kernel test >>>> robot or from Dan? >> >> /* >> * Once FDT buffer has been successfully passed to >> kexec_add_buffer(), >> * the FDT buffer address is saved in image->arch.fdt. In that >> case, >> * the memory cannot be freed here in case of any other error. >> */ >> if (ret && !image->arch.fdt) >> kvfree(fdt); >> >> return ret ? ERR_PTR(ret) : NULL; >> >> In case of an error, the memory allocated for fdt is freed unless it has >> already been passed to kexec_add_buffer(). > = > It feels like the root of the problem is that the kvfree of fdt is in > the wrong place. It's only allocated later in the function, so the error > path should reflect that. Something like the patch below. > = > cheers > = > = > diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c > index 5a569bb51349..02662e72c53d 100644 > --- a/arch/powerpc/kexec/elf_64.c > +++ b/arch/powerpc/kexec/elf_64.c > @@ -114,7 +114,7 @@ static void *elf64_load(struct kimage *image, char *k= ernel_buf, > ret =3D setup_new_fdt_ppc64(image, fdt, initrd_load_addr, > initrd_len, cmdline); > if (ret) > - goto out; > + goto out_free_fdt; > = > fdt_pack(fdt); > = > @@ -125,7 +125,7 @@ static void *elf64_load(struct kimage *image, char *k= ernel_buf, > kbuf.mem =3D KEXEC_BUF_MEM_UNKNOWN; > ret =3D kexec_add_buffer(&kbuf); > if (ret) > - goto out; > + goto out_free_fdt; > = > /* FDT will be freed in arch_kimage_file_post_load_cleanup */ > image->arch.fdt =3D fdt; > @@ -140,18 +140,14 @@ static void *elf64_load(struct kimage *image, char = *kernel_buf, > if (ret) > pr_err("Error setting up the purgatory.\n"); > = > + goto out; > + > +out_free_fdt: > + kvfree(fdt); > out: > kfree(modified_cmdline); > kexec_free_elf_info(&elf_info); > = > - /* > - * Once FDT buffer has been successfully passed to kexec_add_buffer(), > - * the FDT buffer address is saved in image->arch.fdt. In that case, > - * the memory cannot be freed here in case of any other error. > - */ > - if (ret && !image->arch.fdt) > - kvfree(fdt); > - > return ret ? ERR_PTR(ret) : NULL; > } > = > = This looks good to me. Thanks Michael. I'll post the updated patch shortly. -lakshmi --===============2035393431708622482==--