From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4E45437F331 for ; Fri, 28 Aug 2026 06:00:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.176 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787896804; cv=none; b=h3fW0YqHcKILdNr+yPh5WS6cij3RG6yAzH/WUUhUAnVUgeg3ZCbOItH6lmjM1kLgIbNlWT1Hc8PoBnpTg4NiSj425dvVyk67Vcw8oNJFwrDUKDtwvYviTsXX6mEA2Z4v7WGsos2Ugd+Oc3Ops4tlq0Qg+kHdncm+W/n/QUPeHmw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787896804; c=relaxed/simple; bh=Y3Pxlkk3hzSYzpWCXoMK+05Swu3IcTLWgfLRWxwUd4g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SWYxRjhZ0hE02tC+04gHGhKOv+TUeOPLt8czrXyWxvxhtgWkE6HPvOWEkcg+2hIYr6iY9hTqXiPJhcAyfNyfiruPLZqejv99MePSaVsFDzWXEWDUQA9NKOpYFy9GPvJ6KDyfrpG8LSZb7aEu2tyrfsOl8L8pIX156ATklk87Xu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=XjMg8G76; arc=none smtp.client-ip=209.85.214.176 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XjMg8G76" Received: by mail-pl1-f176.google.com with SMTP id d9443c01a7336-2d71a50caa9so8314755ad.0 for ; Thu, 27 Aug 2026 23:00:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1787896803; x=1788501603; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=CxXRXO9cihd6J9ek1BtX6/zY0HVJ8iMxbQFVA3IYgog=; b=XjMg8G76FUW7yVRFQqU1SDmLhsJsOwW45apqogrsrFWo/aYUSy1XgQhM0c+Y40rJpF Zr1TQPAEYDuQZcCghWFKdkSktxfmUSbwRRgycQdlMsuwzAQY0xER8FJSJz1qZtbtyA/Y rJ3R0hAis0TutAI+XL6gaSbsLFjf8xlDsTKXTWryf9ZnwpEvqCqIZ0hblVL9h5IdA1x3 SkG6hSbCtFPszh7AwrCaNk4Xc6goiygHv4acyCi3IkPaTyBIIauo/k+yxv5FOjB2I/hc KDlukGYCsSm7UROFHDJjIPVMEYjA/oTzAYipo/hdgXRMMHJe+npEIk+C5Pk7PBdhifxK l3hw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787896803; x=1788501603; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=CxXRXO9cihd6J9ek1BtX6/zY0HVJ8iMxbQFVA3IYgog=; b=pJNJyOS//XM38bJdG/kAIowtb16ru9cbXtw90CgBsV4wvesYiWXBo2jRwDWUSEMnPg KHr0ANcSfrO9Z++9SZKEtj5Mx9oT9UwBVAH18mUK7pxLui5KnPYcVTq6okgT35h1kp4c Z7tu51ExC9WoiqdM/JO2uX+f6hSU9gnCLaOzBPYIOcrXBbRuw7tPwLNtwGhvsTQUHoW4 OyK4yZMVBlNT5DtlkgYRAuslg+vckUK0iqNDwG1qpN0Fmgaoe+D7DdOdBW6Tj9AISlE9 s/dq2YMsiDpUgbMZokJuW89M1Tm+qYAmwy5zyC8GWwdKf3MAHXkqTieeFvpnLpQUe1jn MH0A== X-Forwarded-Encrypted: i=1; AHgh+RocucAFJcQRmL8NzT2mDVzNFxkZj5SwXsvTboKjH2PQi9ZgN6rgjs/H5TJ17JvH2V8BK1C54Ef2IZAd+SQ=@vger.kernel.org X-Gm-Message-State: AFuF++meSH8SWhDPKLD85gsHTLas6TOJ88c0UOn5Fc+E7S86cHAkuA7H 5/52DD7OadOn2kzNrKDQvlvTR06Vjx6GXuVycTiXYoJTMNnTEjC/RuxS X-Gm-Gg: AR+sD12tc3zJshofPJi8jWkPvtpMWuypcvRDv9AHjV7qdxHRpvvoyyLpM2YeWC+xPLm YI5R+a9elify9mfoCU7pSqN3NqeYiC2XaVMSIbFHhjEyCryZnD2uq0ZqZo/k/5zffhAE5D5QDPs sgEbBuYFC/w2yjIe0yKwd0VHgnFCXW0hHdk82k9GK8ItRXMOAxwMWFM8muIPkOul8Zz2wW6JBOI 4gGlklxTwrBohpAYr2BE2w8lw7W0gBjfRB1C+Twku3ezhCyI8iWxEuXuNt9H187dYRi5ly93eyB 2klpH+8Ck/DNCeh9Ha/11Fix290UoRAsWKZPWOxOe6/Myn54cg5Gmwf1mRoXGjLApjDnc5OM6mW yE18gBFcKW4BzKOW8BH9diFjw4ieLDJOjmus/SvYq9fXMcTxiqv0/9x6reAd4KvcrLQQ83S7HF2 33xVgYQ3RC8g+lzT2F2mJFxh8TyAYzJtWO7AARgesh8wbE9zo7yzyzg2Yr2yM6kD8ksNAUmTvLm gk= X-Received: by 2002:a17:90b:264c:b0:396:61f1:da5c with SMTP id 98e67ed59e1d1-396d0e86577mr9497339a91.4.1787896802700; Thu, 27 Aug 2026 23:00:02 -0700 (PDT) Received: from localhost.localdomain ([240e:b8f:1df9:a600:c693:b19f:ada0:748]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-396b0ea808csm5826241a91.2.2026.08.27.22.59.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Aug 2026 23:00:02 -0700 (PDT) From: Vernon Yang To: akpm@linux-foundation.org, david@kernel.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 Subject: [PATCH v4 3/3] mm: khugepaged: fix folio is used after folio_put/unlock() Date: Fri, 28 Aug 2026 13:59:26 +0800 Message-ID: <20260828055926.346744-4-vernon2gm@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260828055926.346744-1-vernon2gm@gmail.com> References: <20260828055926.346744-1-vernon2gm@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Acked-by: Lorenzo Stoakes (ARM) 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 | 4 +++- 2 files changed, 6 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 4d360ae87769..52b4476898d9 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2256,6 +2256,7 @@ 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); @@ -2275,6 +2276,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, result = alloc_charge_folio(&new_folio, mm, cc, HPAGE_PMD_ORDER); if (result != SCAN_SUCCEED) goto out; + new_pfn = folio_pfn(new_folio); mapping_set_update(&xas, mapping); @@ -2678,7 +2680,7 @@ static enum scan_result collapse_file(struct mm_struct *mm, unsigned long addr, folio_put(new_folio); out: VM_BUG_ON(!list_empty(&pagelist)); - trace_mm_khugepaged_collapse_file(mm, new_folio, index, addr, is_shmem, file, HPAGE_PMD_NR, result); + trace_mm_khugepaged_collapse_file(mm, new_pfn, index, addr, is_shmem, file, HPAGE_PMD_NR, result); return result; } -- 2.53.0