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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D32F8ECAAD4 for ; Sat, 3 Sep 2022 10:27:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229594AbiICK1E (ORCPT ); Sat, 3 Sep 2022 06:27:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54320 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229580AbiICK1C (ORCPT ); Sat, 3 Sep 2022 06:27:02 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2D99685FD3; Sat, 3 Sep 2022 03:27:01 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B4F9F6117C; Sat, 3 Sep 2022 10:27:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CD9CC433D6; Sat, 3 Sep 2022 10:26:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662200820; bh=/IkOHTF9lucJ4Y99Dr1BxXHUQdq8etcVyuS/Yk89Wyc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rPa5BjtxltcjWbQXmWghhBoBiNPSzrR9PnqQIZGHiRS8vfJ1Ym61qhJIIem4RBVzX FtenwaiWBRWJ7rGOTBR4WPMqdHyQJmWzIIBJPFcm2+WyA1Hi4JLkDlIS+yRNngNj3I OCmUqeBUIP77u2iqB2MM1/5DwcXKipVvak0kf1v49FVK4ylaPwGXiDWc+68VR8T9yT 0WxcnLoKZVPO3wQQ+PEDbLxkNKwkGJS/Ch/DH7slJkjmOyCB/x2mVkayAyLMCqbtQ8 ckGjQwyj+b58sKUO9OjMZyT+maWqg0k+D0Lz+g+6hv14GI4dsIl4DBk4MiCPW3WRPN n7B91Mb/zHPzg== Date: Sat, 3 Sep 2022 13:26:54 +0300 From: Jarkko Sakkinen To: linux-sgx@vger.kernel.org Cc: Haitao Huang , Vijay Dhanraj , Reinette Chatre , Dave Hansen , Paul Menzel , stable@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 1/2] x86/sgx: Do not fail on incomplete sanitization on premature stop of ksgxd Message-ID: References: <20220903060108.1709739-1-jarkko@kernel.org> <20220903060108.1709739-2-jarkko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220903060108.1709739-2-jarkko@kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Sep 03, 2022 at 09:01:07AM +0300, Jarkko Sakkinen wrote: > Unsanitized pages trigger WARN_ON() unconditionally, which can panic the > whole computer, if /proc/sys/kernel/panic_on_warn is set. > > In sgx_init(), if misc_register() fails or misc_register() succeeds but > neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be > prematurely stopped. This may leave unsanitized pages, which will result a > false warning. > > Refine __sgx_sanitize_pages() to return: > > 1. Zero when the sanitization process is complete or ksgxd has been > requested to stop. > 2. The number of unsanitized pages otherwise. > > Use the return value as the criteria for triggering output, and tone down > the output to pr_err() to prevent the whole system to be taken down if for > some reason sanitization process does not complete. > > Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u > Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list") > Cc: stable@vger.kernel.org # v5.13+ > Reported-by: Paul Menzel > Signed-off-by: Jarkko Sakkinen > --- > v7: > - Rewrote commit message. > - Do not return -ECANCELED on premature stop. Instead use zero both > premature stop and complete sanitization. > > v6: > - Address Reinette's feedback: > https://lore.kernel.org/linux-sgx/Yw6%2FiTzSdSw%2FY%2FVO@kernel.org/ > > v5: > - Add the klog dump and sysctl option to the commit message. > > v4: > - Explain expectations for dirty_page_list in the function header, instead > of an inline comment. > - Improve commit message to explain the conditions better. > - Return the number of pages left dirty to ksgxd() and print warning after > the 2nd call, if there are any. > > v3: > - Remove WARN_ON(). > - Tuned comments and the commit message a bit. > > v2: > - Replaced WARN_ON() with optional pr_info() inside > __sgx_sanitize_pages(). > - Rewrote the commit message. > - Added the fixes tag. > --- > arch/x86/kernel/cpu/sgx/main.c | 33 ++++++++++++++++++++++++++------- > 1 file changed, 26 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index 515e2a5f25bb..c0a5ce19c608 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -49,17 +49,23 @@ static LIST_HEAD(sgx_dirty_page_list); > * Reset post-kexec EPC pages to the uninitialized state. The pages are removed > * from the input list, and made available for the page allocator. SECS pages > * prepending their children in the input list are left intact. > + * > + * Contents of the @dirty_page_list must be thread-local, i.e. > + * not shared by multiple threads. > + * > + * Return 0 when sanitization was successful or kthread was stopped, and the > + * number of unsanitized pages otherwise. > */ > -static void __sgx_sanitize_pages(struct list_head *dirty_page_list) > +static unsigned long __sgx_sanitize_pages(struct list_head *dirty_page_list) > { > + unsigned long left_dirty = 0; > struct sgx_epc_page *page; > LIST_HEAD(dirty); > int ret; > > - /* dirty_page_list is thread-local, no need for a lock: */ > while (!list_empty(dirty_page_list)) { > if (kthread_should_stop()) > - return; > + return 0; > > page = list_first_entry(dirty_page_list, struct sgx_epc_page, list); > > @@ -92,12 +98,14 @@ static void __sgx_sanitize_pages(struct list_head *dirty_page_list) > } else { > /* The page is not yet clean - move to the dirty list. */ > list_move_tail(&page->list, &dirty); > + left_dirty++; > } > > cond_resched(); > } > > list_splice(&dirty, dirty_page_list); > + return left_dirty; > } > > static bool sgx_reclaimer_age(struct sgx_epc_page *epc_page) > @@ -388,17 +396,28 @@ void sgx_reclaim_direct(void) > > static int ksgxd(void *p) > { > + unsigned long left_dirty; > + > set_freezable(); > > /* > * Sanitize pages in order to recover from kexec(). The 2nd pass is > * required for SECS pages, whose child pages blocked EREMOVE. > */ > - __sgx_sanitize_pages(&sgx_dirty_page_list); > - __sgx_sanitize_pages(&sgx_dirty_page_list); > + left_dirty = __sgx_sanitize_pages(&sgx_dirty_page_list); > + pr_debug("%ld unsanitized pages\n", left_dirty); %lu > > - /* sanity check: */ > - WARN_ON(!list_empty(&sgx_dirty_page_list)); > + left_dirty = __sgx_sanitize_pages(&sgx_dirty_page_list); > + /* > + * Never expected to happen in a working driver. If it happens the bug > + * is expected to be in the sanitization process, but successfully > + * sanitized pages are still valid and driver can be used and most > + * importantly debugged without issues. To put short, the global state > + * of kernel is not corrupted so no reason to do any more complicated > + * rollback. > + */ > + if (left_dirty) > + pr_err("%ld unsanitized pages\n", left_dirty); %lu > > while (!kthread_should_stop()) { > if (try_to_freeze()) > -- > 2.37.2 > BR, Jarkko