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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A547DC433E1 for ; Tue, 30 Jun 2020 17:14:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8064020723 for ; Tue, 30 Jun 2020 17:14:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="fXh+iFaN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390096AbgF3ROC (ORCPT ); Tue, 30 Jun 2020 13:14:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50828 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388029AbgF3ROC (ORCPT ); Tue, 30 Jun 2020 13:14:02 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 90C0CC061755 for ; Tue, 30 Jun 2020 10:14:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=h9dCCR3Sj6ij6SAKyMivwVidTMWb8VV+xdCxCmwqbSc=; b=fXh+iFaNONuimn4tWMRlR/6hmp NY/76oKPggzRBi/jIsdgk7mvxkr0cwOqMmnpVpVU5Q1+lDO+heYD0v6KI7lN2X2jo+d7eXCCCCeQR JsQzfndrVwIGu8KrfiV3lYN77kstxuFLTQlUGqXcIkpASY2Boh2233xagOBrkyGnSoBpROnzu+5Js cHoTDWjyZe8O7Yt/YOlbriW0qp3LBYN9FbDUYDUiFPgCu/AMchFgbWDiGDKhYZbCIeiDoxxMM/njk Y/8Ns5hf97hfID3VfOxJkSUcnPQQNFNTmCuaFZe2JF2B1X9W1EcVQoC3KE/qeC2cipS8AKuEjFkKL t+7HwSig==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jqJpP-0003YN-Lz; Tue, 30 Jun 2020 17:13:52 +0000 Date: Tue, 30 Jun 2020 18:13:51 +0100 From: Matthew Wilcox To: Long Li Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm, slab: Check GFP_SLAB_BUG_MASK before alloc_pages in kmalloc_order Message-ID: <20200630171351.GO25523@casper.infradead.org> References: <20200630145155.GA52108@lilong> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200630145155.GA52108@lilong> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 30, 2020 at 02:51:55PM +0000, Long Li wrote: > In the ARM32 environment with highmem enabled. Using flag of kmalloc() > with __GFP_HIGHMEM to allocate large memory, it will go through the > kmalloc_order() path and return NULL. The __GFP_HIGHMEM flag will > cause alloc_pages() to allocate highmem memory and pages cannot be > directly converted to a virtual address, kmalloc_order() will return > NULL and the page has been allocated. > > After modification, GFP_SLAB_BUG_MASK has been checked before > allocating pages, refer to the new_slab(). > > Signed-off-by: Long Li > --- > > Changes in v2: > - patch is rebased againest "[PATCH] mm: Free unused pages in > kmalloc_order()" [1] > - check GFP_SLAB_BUG_MASK and generate warnings before alloc_pages > in kmalloc_order() > > [1] https://lkml.org/lkml/2020/6/27/16 > > mm/slab_common.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index a143a8c8f874..3548f4f8374b 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -27,6 +27,7 @@ > #include > > #include "slab.h" > +#include "internal.h" > > enum slab_state slab_state; > LIST_HEAD(slab_caches); > @@ -815,6 +816,15 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order) > void *ret = NULL; > struct page *page; > > + if (unlikely(flags & GFP_SLAB_BUG_MASK)) { > + gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK; > + > + flags &= ~GFP_SLAB_BUG_MASK; > + pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", > + invalid_mask, &invalid_mask, flags, &flags); > + dump_stack(); > + } > + > flags |= __GFP_COMP; Oh, this is really good! I hadn't actually looked at how slab/slub handle GFP_SLAB_BUG_MASK. If you don't mind though, I would suggest that this code should all be in one place. Perhaps: gfp_t kmalloc_invalid_flags(gfp_t flags) { gfp_t invalid_mask = flags & GFP_SLAB_BUG_MASK; flags &= ~GFP_SLAB_BUG_MASK; pr_warn("Unexpected gfp: %#x (%pGg). Fixing up to gfp: %#x (%pGg). Fix your code!\n", invalid_mask, &invalid_mask, flags, &flags); dump_stack(); return flags; } and then call it from the three places? Also, the changelog could do with a bit of work. Perhaps: kmalloc cannot allocate memory from HIGHMEM. Allocating large amounts of memory currently bypasses the check and will simply leak the memory when page_address() returns NULL. To fix this, factor the GFP_SLAB_BUG_MASK check out of slab & slub, and call it from kmalloc_order() as well.