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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 76B52C5478C for ; Sat, 2 Mar 2024 00:17:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=k+5GFQEGM/YpzvKfTm6sch32ayN4A0R/Xe/ppJwQ9yk=; b=T2+i+Gx9PIQtq2 eboEChB6+q5Nx1EisW28ThBLHPUo22bzqlDslvBHRAndpNbkUkXSrZlpv9QL7behiQq9J4BMfJ2Lh ueFVSBHTkAWu887xvN/g4CVU4MUMzP8A3GYpT8h3k3/RPRjz4MyHJW+sh3k6QMS+NSNwZrDJrn2OA +xZzT++PsbA34sKFIRpvqCczOsjdyQj8WebBNegI9B5EfNTW974A7oT6ubpvNjeA0DsQ5Xe10MfKg ippX+/WbBEQPnFUREbmHQZTvWgFOJJJdoeaCm1xG4C91eG9g9Tti4BwO+8XGDcxByRKsviu0HO+yv BOdtHHWbxLhDgxouN37g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rgD4J-00000002M6C-3PHI; Sat, 02 Mar 2024 00:17:35 +0000 Received: from mgamail.intel.com ([198.175.65.15]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rgD4E-00000002LyU-3WcE for linux-snps-arc@lists.infradead.org; Sat, 02 Mar 2024 00:17:33 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1709338650; x=1740874650; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Q8lflewJVvOA/SjbcwAPzcjdYdEV2au8S/4Oa3Is2uY=; b=G87juToBfFY4qrOO2F3vTT61AWU07TruD6momwVMnJc0RvB/RmzBu1dj cjNC/tIxezVv4wEJHzpjTufiOeN85aW5DtlnhYvHMA4Rlh4q6dN9O8fNo aqqEk+Sw4niKZ8AngQUAoh3Ig7bcgUdsKpPCzvWML0km1TDF7Fe2wlDPa /J1VCk8XF6KNZdaAudzM/UdIsot4l46b6VwxSYPaCZE++4g9GecInrv6z BONLieEXidtL2eOj0uvU/T7FswwBb7rbDhUFQQ4JWiiSNwKyy8lhGrURT MZlD7Oefi9EWXte0vvasXkD9tkAsn+gSUVw2+fUUuI/o6YZdOBFyQLFyz A==; X-IronPort-AV: E=McAfee;i="6600,9927,11000"; a="7715671" X-IronPort-AV: E=Sophos;i="6.06,197,1705392000"; d="scan'208";a="7715671" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Mar 2024 16:17:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.06,197,1705392000"; d="scan'208";a="8495944" Received: from thwood-mobl1.amr.corp.intel.com (HELO rpedgeco-desk4.intel.com) ([10.251.7.75]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Mar 2024 16:17:21 -0800 From: Rick Edgecombe To: rick.p.edgecombe@intel.com Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org, bp@alien8.de, broonie@kernel.org, dave.hansen@linux.intel.com, debug@rivosinc.com, hpa@zytor.com, keescook@chromium.org, kirill.shutemov@linux.intel.com, luto@kernel.org, mingo@redhat.com, peterz@infradead.org, sparclinux@vger.kernel.org, tglx@linutronix.de, x86@kernel.org, Vineet Gupta , linux-snps-arc@lists.infradead.org Subject: [RFC v2.1 01/12] ARC: Use initializer for struct vm_unmapped_area_info Date: Fri, 1 Mar 2024 16:17:03 -0800 Message-Id: <20240302001714.674091-1-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240226190951.3240433-6-rick.p.edgecombe@intel.com> References: <20240226190951.3240433-6-rick.p.edgecombe@intel.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240301_161731_007518_81BABA0D X-CRM114-Status: GOOD ( 15.94 ) X-BeenThere: linux-snps-arc@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux on Synopsys ARC Processors List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-snps-arc" Errors-To: linux-snps-arc-bounces+linux-snps-arc=archiver.kernel.org@lists.infradead.org Future changes will need to add a new member to struct vm_unmapped_area_info. This would cause trouble for any call site that doesn't initialize the struct. Currently every caller sets each field manually, so if new fields are added they will be unitialized and the core code parsing the struct will see garbage in the new field. It could be possible to initialize the new field manually to 0 at each call site. This and a couple other options were discussed, and the consensus (see links) was that in general the best way to accomplish this would be via static initialization with designated field initiators. Having some struct vm_unmapped_area_info instances not zero initialized will put those sites at risk of feeding garbage into vm_unmapped_area() if the convention is to zero initialize the struct and any new field addition misses a call site that initializes each field manually. It could be possible to leave the code mostly untouched, and just change the line: struct vm_unmapped_area_info info to: struct vm_unmapped_area_info info = {}; However, that would leave cleanup for the fields that are manually set to zero, as it would no longer be required. So to be reduce the chance of bugs via uninitialized fields, instead simply continue the process to initialize the struct this way tree wide. This will zero any unspecified members. Move the field initializers to the struct declaration when they are known at that time. Leave the fields out that were manually initialized to zero, as this would be redundant for designated initializers. Signed-off-by: Rick Edgecombe Cc: Vineet Gupta Cc: linux-snps-arc@lists.infradead.org Link: https://lore.kernel.org/lkml/202402280912.33AEE7A9CF@keescook/#t Link: https://lore.kernel.org/lkml/j7bfvig3gew3qruouxrh7z7ehjjafrgkbcmg6tcghhfh3rhmzi@wzlcoecgy5rs/ --- Hi, This patch was split and refactored out of a tree-wide change [0] to just zero-init each struct vm_unmapped_area_info. The overall goal of the series is to help shadow stack guard gaps. Currently, there is only one arch with shadow stacks, but two more are in progress. It is 0day tested only. Thanks, Rick [0] https://lore.kernel.org/lkml/20240226190951.3240433-6-rick.p.edgecombe@intel.com/ --- arch/arc/mm/mmap.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/arch/arc/mm/mmap.c b/arch/arc/mm/mmap.c index 3c1c7ae73292..9c8b3d1d7bfb 100644 --- a/arch/arc/mm/mmap.c +++ b/arch/arc/mm/mmap.c @@ -27,7 +27,12 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; - struct vm_unmapped_area_info info; + struct vm_unmapped_area_info info = { + .length = len, + .low_limit = mm->mmap_base, + .high_limit = TASK_SIZE, + .align_offset = pgoff << PAGE_SHIFT + }; /* * We enforce the MAP_FIXED case. @@ -51,12 +56,6 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, return addr; } - info.flags = 0; - info.length = len; - info.low_limit = mm->mmap_base; - info.high_limit = TASK_SIZE; - info.align_mask = 0; - info.align_offset = pgoff << PAGE_SHIFT; return vm_unmapped_area(&info); } -- 2.34.1 _______________________________________________ linux-snps-arc mailing list linux-snps-arc@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-snps-arc