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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4E1B3C36010 for ; Tue, 1 Apr 2025 21:09:43 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EFABE280003; Tue, 1 Apr 2025 17:09:41 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E8097280001; Tue, 1 Apr 2025 17:09:41 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D219D280003; Tue, 1 Apr 2025 17:09:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id B4033280001 for ; Tue, 1 Apr 2025 17:09:41 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 19CC5B7419 for ; Tue, 1 Apr 2025 21:09:42 +0000 (UTC) X-FDA: 83286716604.17.191E6C4 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf28.hostedemail.com (Postfix) with ESMTP id 6734FC000B for ; Tue, 1 Apr 2025 21:09:40 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=U9FAPaRP; dmarc=none; spf=pass (imf28.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1743541780; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=nvkBP12pZGSxPYA4RMY/cPoutRroVZDrieVt/b5u7Fg=; b=KcY/mpcdy0o4ndPb3+9IvoK5SwSRY4LLZtmmpZYSkXIL64dRAx6TeKthtoLLiSN5DlCGB7 sSDHmTJIsvaFgdn50e4WKCT0YVx+W7hjDUCfd9fb0t0KoNM3zMeGuWWQSBaf7QWguWibxF vUw6lA6Jsip8FJN41azEVkFtVhWNrww= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1743541780; a=rsa-sha256; cv=none; b=OsLkxaU2ey+Xyyz2Pv7+0gVfH4Q7yq/IB6aGHwCTDU/U3wigldD5jc6+04F2DHYZuRb7V8 bOzuVX/4SAPL9klmBvU3WWSE2wOHFzMLp8av7h+4/GlmorM6Hxpfmp5qDB7f3kHlY7q/h3 9bto77uWkB2XYYSpuOSacOJLSnt6BEw= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=U9FAPaRP; dmarc=none; spf=pass (imf28.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 45CF75C5BDE; Tue, 1 Apr 2025 21:07:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C25B0C4CEE4; Tue, 1 Apr 2025 21:09:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1743541778; bh=g/G+eELwpWY77gtLoCFC2tBGw0PqTU+QAnrfU5ji81E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=U9FAPaRPiRo/5rzbNux9QLswWSjCfjH+EmFPZS8VFR8N3kL6gUsAZuvgFagXWMbEs hd50Zv8mX9t+0nE/iCJRnycm/PyaBvPL7ZX1i5iAfsaq28KCgZURpCq9E0ORSe1sIm CCAG8x/QiYuAZxaYIbSnDNwTzp5UC16sFCdLXb58= Date: Tue, 1 Apr 2025 14:09:38 -0700 From: Andrew Morton To: Sweet Tea Dorminy Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/khugepaged: fix a tracepoint for error cases Message-Id: <20250401140938.34993d9922eb1e71ba2b2ff8@linux-foundation.org> In-Reply-To: <20250401202354.103501-2-sweettea-kernel@dorminy.me> References: <20250401202354.103501-2-sweettea-kernel@dorminy.me> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 6734FC000B X-Stat-Signature: m1b9tapzrek33sdzubq4hz3hktx6bbmd X-Rspam-User: X-HE-Tag: 1743541780-957423 X-HE-Meta: U2FsdGVkX1+lF5J/4AFh6mOnrUdVhaqQ+Zm/9CoCff8Xs2Q9iVMvffMhEP3e7JmkAEu9QQgemb0wX3V1naRDySa5LRx+4IRL/sla6ZvHWgUVjB3efHn9nm1NffJzczGbXN00FsZVpvtPVeieiQHtPL74fX2WXurhV93Z1BRO7BjzXbHcG0mEDYsG8ToSt7u9Az7FMw1vHDCtTPAHKy50zEgnju2+c3B+wrFPVBCEdIf515LdL5brWJt2fgCxLi8h8z8a2WEoxQ14f2aBwDtEoMASAmvXVjGhDGX7EzSVoZ5SjidtFbG2Jvzt8rc4diGZ4rJ41K4e1YTEq1fgljWUh+Qodu01Ul3Za5ShXleZ9NIJBKQIG2TonPDbUy+FVcJRFrysa7UOzJ5El8yQboOryAfRtW+EsFsJkpnWHkOd5rIHGFLVXeLasdx45hPwZVwqst7Uj81Idp5foVpUebqS6NMwf6eRHICOZ+0J9niuDLhcjGsTY48HF3b8crVz4FOSaX48+BjR64y24H2Rn6PXL3iqxdA6DFSfRqgOxpC6iZJfp48lAb5X2HKQu0d+XSWa7CqoFOCKx9SRbq+91LQhIX/qYGi4/O9aCoM+fIwq9ocCWuLVwyg2NtyvDUy9cEuZxmuuPXCQ1F47KsRF6r7WS6py4bXJ5vfOdd65D9tm2Ht+an0m34AFC9DAF0fFemS2OuCctSNsYpWHgLAdRRuQ5kbvk9C9dnahHQ3b1zdvN0UcGSBw/XxnYoMAciKeXe+uVk7hX41YbZur5PF8fSZfz8krZXfWKznRmSljOEGt13gcwtB33ZUuzA7CW+l4nYOc5KyVV2avAeNDc7squ215w5veOg49b2XOO4mH5I4U2Mz/d3fQ5la2mODqoL5vcUajuqdci+CMW2OPfSzXzJdqVPH/ZlvrQaBO0IJi+hFdDyLz/6gG1hbc1U/gsbm5NTBDpv1nYiuw3oahXwhRKmN iFy15wfi BDfo2/xNBsU/A9P0DrxcCNEdhod1e66/HzRdjgJME6H5zvR61dyGhFAo8uzW6Pij9q6UnBA+vMTfR8e1zEwNHRKLzyPJtaSWkDA6EZaSjHd3By4QkSr07o9wDbA5FZ/yMXngjdo2iEwW6bBsTtVUFQul7Y4VTPHcRjHBsimpnSgDqjQy8tuM722MhaCFpFcJpXRB2ouwTJuxweFGtJMkOeYE36jeFktEsjgZwG0PR1eUkA1pQiMxwXMBIPw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 1 Apr 2025 16:23:53 -0400 Sweet Tea Dorminy wrote: > Fix a potential NULL pointer dereference in trace_mm_khugepaged_scan_pmd() > when folio is NULL. This is possible if vm_normal_page() returned a NULL > page -- which is unlikely, but was hit in testing. > > (The tracepoint in include/trace/events/huge_memory.h can already deal > with a NULL page.) > > ... > > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1435,8 +1435,9 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm, > *mmap_locked = false; > } > out: > - trace_mm_khugepaged_scan_pmd(mm, &folio->page, writable, referenced, > - none_or_zero, result, unmapped); > + trace_mm_khugepaged_scan_pmd(mm, folio ? &folio->page : NULL, > + writable, referenced, none_or_zero, > + result, unmapped); > return result; Confused. If folio==NULL then &folio->page==NULL also. The patch appears to be a no-op? Do you have the messages from that oops?