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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 33197C5DF94 for ; Mon, 24 Aug 2026 12:00:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3404D6B008C; Mon, 24 Aug 2026 08:00:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2F1016B009B; Mon, 24 Aug 2026 08:00:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DFCA6B009D; Mon, 24 Aug 2026 08:00:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id E67296B008C for ; Mon, 24 Aug 2026 08:00:02 -0400 (EDT) Received: from smtpin23.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 6EA3F80494 for ; Mon, 24 Aug 2026 12:00:02 +0000 (UTC) X-FDA: 85136019444.23.BB93160 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf27.hostedemail.com (Postfix) with ESMTP id A033540006 for ; Mon, 24 Aug 2026 12:00:00 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DV8XUbma; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787572800; b=xcTFQaoEI1D8QlvFtzs44/krLIXd71rVwhTucOlkgzFFceG5FKdguDtTV4qocE0Cw5jfPQ OhVbAh8BNwPaTnBjZMqnSlg8d3MSE6RAJYxR+LsaYFLF28hCcbL4Q/v70U5/6w1xj/vU8U rQIo6Z1UZDQh1tDLxQAPyIA/4aRun/I= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=DV8XUbma; spf=pass (imf27.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787572800; 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=rTuYvF3Mu7p31xlyX3il8puWDUAl1lur7TZTZMOinSw=; b=nenFEolLpTysAKxzJbteqtyUA/iixFTzO4ohP7cHZbXtgKafHKVPM6OZnh/CnpI+pc3Vc/ hWHKgWfV2e+5vN3AU9VEPyafUmfhKD9o9qAwaIKfNS4dFIdt1AyHvXjBIes6EUTvciq4Wu s55AysM3Y9WQvBBEywItLY9hDVzaQfs= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C12A940A1D; Mon, 24 Aug 2026 11:59:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3691D1F000E9; Mon, 24 Aug 2026 11:59:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787572799; bh=rTuYvF3Mu7p31xlyX3il8puWDUAl1lur7TZTZMOinSw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=DV8XUbmaKUGJZhyQ1aHYwN/aGyQChNpP/e/L2YUvyE4Qt2E6lWjS7DsjwkPQCtXPu 11Dgzi+rcPEI2V8DfmdRO+2hM6TZmmOOOCZW+MtGDSp/Iw5jx/tyEPab/lS3768PXt +coJPLqdOA25xoeeLV6zmReX18s1vkXtEyAPQLCTUCl82xr1GdOrVHx073h1aGx3rH IyBrhiIRf77corKNQlykvoVSUJd8TtjLwOLjVZxf4TKijbBl/XOCDUPTu1okWd+VlW NhdOqmSULDHu45jlzUp2eCPONjeTRfoA19bjWYycWlWQp21DAEhUrl4VDPmqbmBmXe zT8NEIkG46Rqg== Message-ID: <8001afe8-84e4-43d4-971b-b23f72070339@kernel.org> Date: Mon, 24 Aug 2026 13:59:53 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/3] mm: khugepaged: fix folio is used after folio_put/unlock() To: Vernon Yang , akpm@linux-foundation.org, ljs@kernel.org Cc: nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, zokeefe@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Vernon Yang References: <20260824092935.73892-1-vernon2gm@gmail.com> <20260824092935.73892-4-vernon2gm@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260824092935.73892-4-vernon2gm@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A033540006 X-Rspam-User: X-Stat-Signature: njpmks48xa8ws4yk6s5cgtuq49d9x64k X-Rspamd-Server: rspam06 X-HE-Tag: 1787572800-444031 X-HE-Meta: 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 5IBnovLx W9GqpH3bTuOll2K+JS8x0xn9qyFJJyM2A+xi2XVZqgHlbnn60wDUwYpacFXlm1qje7lo0chbqZecdmVjUobRcaUeN03ZD706z/bMvn+q3DmMSoj5epAv0adgVJadydzynj/P1oony25Ns07jXt2o86KmFu9JrzPsG6KVWJgYNcmXPMhmBrzeajVvRDJEoAavGvI3KKTf/OV6rNJqxD4/OXQKnCXDfdGXtDquOVz15w+9PcAfISj3+Leuz3ww7BvScZWL5uXZJtlCgshjavFqCqgfGxl1QnTmW9hxiVQSbQlFTnlezCZG5crhJPA6v0a+M4e3618Hen310w/I= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/24/26 11:29, Vernon Yang wrote: > From: Vernon Yang > > On the rollback path, folio_put() has already dropped the last reference > of new_folio. On the success path, new_folio is already unlocked and can > be freed concurrently. The trace_mm_khugepaged_collapse_file() is left > with a dangling folio pointer. > > So using the folio_pfn() before dropping the reference, closing > use-after-free window. > > Fixes: 4c9473e87e75 ("mm/khugepaged: add tracepoint to collapse_file()") > Cc: stable@vger.kernel.org > Signed-off-by: Vernon Yang > --- > include/trace/events/huge_memory.h | 6 +++--- > mm/khugepaged.c | 5 ++++- > 2 files changed, 7 insertions(+), 4 deletions(-) > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h > index fa828967e1fb..5fb4d92cfd84 100644 > --- a/include/trace/events/huge_memory.h > +++ b/include/trace/events/huge_memory.h > @@ -211,10 +211,10 @@ TRACE_EVENT(mm_khugepaged_scan_file, > ); > > TRACE_EVENT(mm_khugepaged_collapse_file, > - TP_PROTO(struct mm_struct *mm, struct folio *new_folio, pgoff_t index, > + TP_PROTO(struct mm_struct *mm, unsigned long new_pfn, pgoff_t index, > unsigned long addr, bool is_shmem, struct file *file, > int nr, int result), > - TP_ARGS(mm, new_folio, index, addr, is_shmem, file, nr, result), > + TP_ARGS(mm, new_pfn, index, addr, is_shmem, file, nr, result), > TP_STRUCT__entry( > __field(struct mm_struct *, mm) > __field(unsigned long, hpfn) > @@ -228,7 +228,7 @@ TRACE_EVENT(mm_khugepaged_collapse_file, > > TP_fast_assign( > __entry->mm = mm; > - __entry->hpfn = new_folio ? folio_pfn(new_folio) : -1; > + __entry->hpfn = new_pfn; > __entry->index = index; > __entry->addr = addr; > __entry->is_shmem = is_shmem; > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 4e0fca5942dd..24347f1a94ae 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2254,6 +2254,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > struct address_space *mapping = file->f_mapping; > struct page *dst; > struct folio *folio, *tmp, *new_folio; > + unsigned long new_pfn = -1; > pgoff_t index = 0, end = start + HPAGE_PMD_NR; > LIST_HEAD(pagelist); > XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); > @@ -2633,6 +2634,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, > retract_page_tables(mapping, start); > if (cc && !cc->is_khugepaged) > result = SCAN_PTE_MAPPED_HUGEPAGE; > + new_pfn = folio_pfn(new_folio); Why not set new_pfn once after successful alloc_charge_folio()? -- Cheers, David