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 8D103C43217 for ; Thu, 17 Nov 2022 14:35:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240502AbiKQOfC (ORCPT ); Thu, 17 Nov 2022 09:35:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58270 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240402AbiKQOeX (ORCPT ); Thu, 17 Nov 2022 09:34:23 -0500 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B1845DB9F for ; Thu, 17 Nov 2022 06:34:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1668695661; x=1700231661; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to; bh=FUaqxpNOUtBFK9yqPq0EtJNjrRCYpDB/RJdLe9Np1/M=; b=Jc22b9bJlaufx0Sqp4ZWP9rMRi3SfMki4l3Rlskz5QbIEplLmo3I84Hw bq+LlAunjKQuBlhbkmiIazNVbDU9OHGmVcUMI70lL8pEtsE0WrfjmGoXV qPKgr1T2FrEAyme4ku4Th/qBTAJjTpvi+xdkEGrd9CuQtFH6LKr4WYy3n xu7DSnO6OEkwSbeYxR+c21GrPc4HHC5Df2scuJTFbI4Dl2n1/fEFekycp HswsBs6JrZxYIRpxxwyInNPhnrgMKWfxZHJHOTVHopAia6J2aov3mld13 z1M5/+H8JFjjM84MLwa4An3O4rePn7uzeSq85RvvMSO74340BCeKsvyNI g==; X-IronPort-AV: E=McAfee;i="6500,9779,10534"; a="399152687" X-IronPort-AV: E=Sophos;i="5.96,171,1665471600"; d="scan'208";a="399152687" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Nov 2022 06:34:16 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10534"; a="814534057" X-IronPort-AV: E=Sophos;i="5.96,171,1665471600"; d="scan'208";a="814534057" Received: from vrgatne-mobl4.amr.corp.intel.com (HELO [10.209.115.197]) ([10.209.115.197]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Nov 2022 06:34:15 -0800 Content-Type: multipart/mixed; boundary="------------5Ob6KInVGuG0YbX9A7MUQQSR" Message-ID: <4208866d-338f-4781-7ff9-023f016c5b07@intel.com> Date: Thu, 17 Nov 2022 06:34:15 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/kfence.h:46 kfence_protect Content-Language: en-US To: Marco Elver , Naresh Kamboju , Peter Zijlstra Cc: kasan-dev , X86 ML , open list , linux-mm , regressions@lists.linux.dev, lkft-triage@lists.linaro.org, Andrew Morton , Alexander Potapenko References: From: Dave Hansen In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------5Ob6KInVGuG0YbX9A7MUQQSR Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/17/22 05:58, Marco Elver wrote: > [ 0.663761] WARNING: CPU: 0 PID: 0 at arch/x86/include/asm/kfence.h:46 kfence_protect+0x7b/0x120 > [ 0.664033] WARNING: CPU: 0 PID: 0 at mm/kfence/core.c:234 kfence_protect+0x7d/0x120 > [ 0.664465] kfence: kfence_init failed Any chance you could add some debugging and figure out what actually made kfence call over? Was it the pte or the level? if (WARN_ON(!pte || level != PG_LEVEL_4K)) return false; I can see how the thing you bisected to might lead to a page table not being split, which could mess with the 'level' check. Also, is there a reason this code is mucking with the page tables directly? It seems, uh, rather wonky. This, for instance: > if (protect) > set_pte(pte, __pte(pte_val(*pte) & ~_PAGE_PRESENT)); > else > set_pte(pte, __pte(pte_val(*pte) | _PAGE_PRESENT)); > > /* > * Flush this CPU's TLB, assuming whoever did the allocation/free is > * likely to continue running on this CPU. > */ > preempt_disable(); > flush_tlb_one_kernel(addr); > preempt_enable(); Seems rather broken. I assume the preempt_disable() is there to get rid of some warnings. But, there is nothing I can see to *keep* the CPU that did the free from being different from the one where the TLB flush is performed until the preempt_disable(). That makes the flush_tlb_one_kernel() mostly useless. Is there a reason this code isn't using the existing page table manipulation functions and tries to code its own? What prevents it from using something like the attached patch? --------------5Ob6KInVGuG0YbX9A7MUQQSR Content-Type: text/x-patch; charset=UTF-8; name="kfence.patch" Content-Disposition: attachment; filename="kfence.patch" Content-Transfer-Encoding: base64 ZGlmZiAtLWdpdCBhL2FyY2gveDg2L2luY2x1ZGUvYXNtL2tmZW5jZS5oIGIvYXJjaC94ODYv aW5jbHVkZS9hc20va2ZlbmNlLmgKaW5kZXggZmY1YzcxMzRhMzdhLi41Y2RiM2ExZjM5OTUg MTAwNjQ0Ci0tLSBhL2FyY2gveDg2L2luY2x1ZGUvYXNtL2tmZW5jZS5oCisrKyBiL2FyY2gv eDg2L2luY2x1ZGUvYXNtL2tmZW5jZS5oCkBAIC0zNywzNCArMzcsMTMgQEAgc3RhdGljIGlu bGluZSBib29sIGFyY2hfa2ZlbmNlX2luaXRfcG9vbCh2b2lkKQogCXJldHVybiB0cnVlOwog fQogCi0vKiBQcm90ZWN0IHRoZSBnaXZlbiBwYWdlIGFuZCBmbHVzaCBUTEIuICovCiBzdGF0 aWMgaW5saW5lIGJvb2wga2ZlbmNlX3Byb3RlY3RfcGFnZSh1bnNpZ25lZCBsb25nIGFkZHIs IGJvb2wgcHJvdGVjdCkKIHsKLQl1bnNpZ25lZCBpbnQgbGV2ZWw7Ci0JcHRlX3QgKnB0ZSA9 IGxvb2t1cF9hZGRyZXNzKGFkZHIsICZsZXZlbCk7Ci0KLQlpZiAoV0FSTl9PTighcHRlIHx8 IGxldmVsICE9IFBHX0xFVkVMXzRLKSkKLQkJcmV0dXJuIGZhbHNlOwotCi0JLyoKLQkgKiBX ZSBuZWVkIHRvIGF2b2lkIElQSXMsIGFzIHdlIG1heSBnZXQgS0ZFTkNFIGFsbG9jYXRpb25z IG9yIGZhdWx0cwotCSAqIHdpdGggaW50ZXJydXB0cyBkaXNhYmxlZC4gVGhlcmVmb3JlLCB0 aGUgYmVsb3cgaXMgYmVzdC1lZmZvcnQsIGFuZAotCSAqIGRvZXMgbm90IGZsdXNoIFRMQnMg b24gYWxsIENQVXMuIFdlIGNhbiB0b2xlcmF0ZSBzb21lIGluYWNjdXJhY3k7Ci0JICogbGF6 eSBmYXVsdCBoYW5kbGluZyB0YWtlcyBjYXJlIG9mIGZhdWx0cyBhZnRlciB0aGUgcGFnZSBp cyBQUkVTRU5ULgotCSAqLwotCiAJaWYgKHByb3RlY3QpCi0JCXNldF9wdGUocHRlLCBfX3B0 ZShwdGVfdmFsKCpwdGUpICYgfl9QQUdFX1BSRVNFTlQpKTsKKwkJc2V0X21lbW9yeV9ucChh ZGRyLCBhZGRyICsgUEFHRV9TSVpFKTsKIAllbHNlCi0JCXNldF9wdGUocHRlLCBfX3B0ZShw dGVfdmFsKCpwdGUpIHwgX1BBR0VfUFJFU0VOVCkpOworCQlzZXRfbWVtb3J5X3AoYWRkciwg YWRkciArIFBBR0VfU0laRSk7CiAKLQkvKgotCSAqIEZsdXNoIHRoaXMgQ1BVJ3MgVExCLCBh c3N1bWluZyB3aG9ldmVyIGRpZCB0aGUgYWxsb2NhdGlvbi9mcmVlIGlzCi0JICogbGlrZWx5 IHRvIGNvbnRpbnVlIHJ1bm5pbmcgb24gdGhpcyBDUFUuCi0JICovCi0JcHJlZW1wdF9kaXNh YmxlKCk7Ci0JZmx1c2hfdGxiX29uZV9rZXJuZWwoYWRkcik7Ci0JcHJlZW1wdF9lbmFibGUo KTsKIAlyZXR1cm4gdHJ1ZTsKIH0KIAo= --------------5Ob6KInVGuG0YbX9A7MUQQSR--