From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A027323C9; Sat, 2 Mar 2024 00:17:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709338646; cv=none; b=XPhRBAAbRkOP6UMK/nTYPMkim1E4JQ7OmVAr4qYQSXFWjX6OLHipwHTkLXei42qSi/GaBpKFtZrQeI2a5m20nDOo6aW/A5KN9Sa5UBnVcF9AID1CMZ8MnDhAiCihYlQgkpo8cvg9VDblcH5igJdJCnSOB5uPuVfr4hJzjEjmmms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709338646; c=relaxed/simple; bh=4HFDwkZQtbRr1bncN2p231qreFYhXShqCQ4Nde6jsro=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=bVqCPpLQ1LNvXG/8mB7rAdamrATD8qhaBO82Ilu2/wDR3r4FJDmtA29JLM4vjW5MIynbtq/GJCX5Ztaf9tPO85Y0rOc6Vjbl8jeLZETPPvLs8v+rv9SzTvAbp3Z/JW37sW6tLGY3YkIcCWw3sFmqfTfpVGUHaFJgYOi9aI77BvY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=IYMUDs9r; arc=none smtp.client-ip=198.175.65.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="IYMUDs9r" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1709338644; x=1740874644; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=4HFDwkZQtbRr1bncN2p231qreFYhXShqCQ4Nde6jsro=; b=IYMUDs9rivvzs3/KbVN1SINAKzthO8ZoMt57iPkz5nGv7m4IFtaLR7/5 /gZ9MtXDibiqJch1jNxmlNtweRIldp/MWlv8bMgdOk8ndE1KjkgqwiEio PnCpaBbOdF5DgYRlcBRywklAWrWgVItGJ4gNUU2BdyZGSh0hJk9nWmgiM xVZrENTeLDfYi9QDAUYfDAmiSu+feysjT37Kkfvg9LfTn19QJ528USj6Q anMpRhulMqtssq2hLkddwgmzihHI+pT8PyoBfnJrNh5lWeperf9VrUkGE AE4hmNZN6aS+ILL/tkAcUW+L16XHLQq03ni8i5D6VSLusuYDOA/y5ISkS w==; X-IronPort-AV: E=McAfee;i="6600,9927,11000"; a="7715696" X-IronPort-AV: E=Sophos;i="6.06,197,1705392000"; d="scan'208";a="7715696" 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 16:17:23 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.06,197,1705392000"; d="scan'208";a="8495960" 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 16:17:22 -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, Guo Ren , linux-csky@vger.kernel.org Subject: [RFC v2.1 03/12] csky: Use initializer for struct vm_unmapped_area_info Date: Fri, 1 Mar 2024 16:17:05 -0800 Message-Id: <20240302001714.674091-3-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240302001714.674091-1-rick.p.edgecombe@intel.com> References: <20240226190951.3240433-6-rick.p.edgecombe@intel.com> <20240302001714.674091-1-rick.p.edgecombe@intel.com> Precedence: bulk X-Mailing-List: linux-csky@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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: Guo Ren Cc: linux-csky@vger.kernel.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/csky/abiv1/mmap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/arch/csky/abiv1/mmap.c b/arch/csky/abiv1/mmap.c index 6792aca49999..7f826331d409 100644 --- a/arch/csky/abiv1/mmap.c +++ b/arch/csky/abiv1/mmap.c @@ -28,7 +28,12 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, struct mm_struct *mm = current->mm; struct vm_area_struct *vma; int do_align = 0; - 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 only need to do colour alignment if either the I or D @@ -61,11 +66,6 @@ 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 = do_align ? (PAGE_MASK & (SHMLBA - 1)) : 0; - info.align_offset = pgoff << PAGE_SHIFT; return vm_unmapped_area(&info); } -- 2.34.1