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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 3BE0CC35280 for ; Fri, 1 May 2020 21:29:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EA7DF208DB for ; Fri, 1 May 2020 21:29:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="R6CJtK8Q" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EA7DF208DB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9EB248E0008; Fri, 1 May 2020 17:29:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 99C458E0001; Fri, 1 May 2020 17:29:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D93A8E0008; Fri, 1 May 2020 17:29:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0093.hostedemail.com [216.40.44.93]) by kanga.kvack.org (Postfix) with ESMTP id 780EA8E0001 for ; Fri, 1 May 2020 17:29:29 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 376C6180AD806 for ; Fri, 1 May 2020 21:29:29 +0000 (UTC) X-FDA: 76769441658.13.year40_52caa697d805a X-HE-Tag: year40_52caa697d805a X-Filterd-Recvd-Size: 7103 Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Fri, 1 May 2020 21:29:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588368568; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ypI/E3zn8fmAPe3GyyyHKXmBOUI7feD3BZfJdMnsdoE=; b=R6CJtK8Q7ZpSP9d/23s+MUm2av2bwiPWdkRaIJkvjEQyH7/c9xOZLA1MGOUlC9x9LiURm+ 3D+lIOPhNG0OGKzoyvuNh+mv+ZiAiFVnYX+QCbcpNBzabHrgiIrqa2O2IU+NYHWtgjmR72 k7NtSmC02hzdVwv/ukgghtJqAs1jZME= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-98-KhZuis_bO_K715ZYxP1zbw-1; Fri, 01 May 2020 17:29:23 -0400 X-MC-Unique: KhZuis_bO_K715ZYxP1zbw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B025C100CCCE; Fri, 1 May 2020 21:29:21 +0000 (UTC) Received: from optiplex-lnx (unknown [10.3.128.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6741A5C1BE; Fri, 1 May 2020 21:29:15 +0000 (UTC) Date: Fri, 1 May 2020 17:29:12 -0400 From: Rafael Aquini To: Waiman Long Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Changbin Du , Matthew Wilcox , Markus Elfring Subject: Re: [PATCH v3] mm/slub: Fix incorrect interpretation of s->offset Message-ID: <20200501212912.GC27720@optiplex-lnx> References: <20200429135328.26976-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200429135328.26976-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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: On Wed, Apr 29, 2020 at 09:53:28AM -0400, Waiman Long wrote: > In a couple of places in the slub memory allocator, the code uses > "s->offset" as a check to see if the free pointer is put right after the > object. That check is no longer true with commit 3202fa62fb43 ("slub: > relocate freelist pointer to middle of object"). > > As a result, echoing "1" into the validate sysfs file, e.g. of dentry, > may cause a bunch of "Freepointer corrupt" error reports like the > following to appear with the system in panic afterwards. > > [ 38.579769] ============================================================================= > [ 38.580845] BUG dentry(666:pmcd.service) (Tainted: G B): Freepointer corrupt > [ 38.581948] ----------------------------------------------------------------------------- > > To fix it, use the check "s->offset == s->inuse" in the new helper > function freeptr_outside_object() instead. Also add another helper function > get_info_end() to return the end of info block (inuse + free pointer > if not overlapping with object). > > Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object") > Signed-off-by: Waiman Long > --- > mm/slub.c | 45 ++++++++++++++++++++++++++++++--------------- > 1 file changed, 30 insertions(+), 15 deletions(-) > > [v3: Change function name to freeptr_outside_object(), update check & add comment] > > diff --git a/mm/slub.c b/mm/slub.c > index 9bf44955c4f1..b762450fc9f0 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -551,15 +551,32 @@ static void print_section(char *level, char *text, u8 *addr, > metadata_access_disable(); > } > > +/* > + * See comment in calculate_sizes(). > + */ > +static inline bool freeptr_outside_object(struct kmem_cache *s) > +{ > + return s->offset >= s->inuse; > +} > + > +/* > + * Return offset of the end of info block which is inuse + free pointer if > + * not overlapping with object. > + */ > +static inline unsigned int get_info_end(struct kmem_cache *s) > +{ > + if (freeptr_outside_object(s)) > + return s->inuse + sizeof(void *); > + else > + return s->inuse; > +} > + > static struct track *get_track(struct kmem_cache *s, void *object, > enum track_item alloc) > { > struct track *p; > > - if (s->offset) > - p = object + s->offset + sizeof(void *); > - else > - p = object + s->inuse; > + p = object + get_info_end(s); > > return p + alloc; > } > @@ -686,10 +703,7 @@ static void print_trailer(struct kmem_cache *s, struct page *page, u8 *p) > print_section(KERN_ERR, "Redzone ", p + s->object_size, > s->inuse - s->object_size); > > - if (s->offset) > - off = s->offset + sizeof(void *); > - else > - off = s->inuse; > + off = get_info_end(s); > > if (s->flags & SLAB_STORE_USER) > off += 2 * sizeof(struct track); > @@ -782,7 +796,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page, > * object address > * Bytes of the object to be managed. > * If the freepointer may overlay the object then the free > - * pointer is the first word of the object. > + * pointer is at the middle of the object. > * > * Poisoning uses 0x6b (POISON_FREE) and the last byte is > * 0xa5 (POISON_END) > @@ -816,11 +830,7 @@ static int check_bytes_and_report(struct kmem_cache *s, struct page *page, > > static int check_pad_bytes(struct kmem_cache *s, struct page *page, u8 *p) > { > - unsigned long off = s->inuse; /* The end of info */ > - > - if (s->offset) > - /* Freepointer is placed after the object. */ > - off += sizeof(void *); > + unsigned long off = get_info_end(s); /* The end of info */ > > if (s->flags & SLAB_STORE_USER) > /* We also have user information there */ > @@ -907,7 +917,7 @@ static int check_object(struct kmem_cache *s, struct page *page, > check_pad_bytes(s, page, p); > } > > - if (!s->offset && val == SLUB_RED_ACTIVE) > + if (!freeptr_outside_object(s) && val == SLUB_RED_ACTIVE) > /* > * Object and freepointer overlap. Cannot check > * freepointer while object is allocated. > @@ -3587,6 +3597,11 @@ static int calculate_sizes(struct kmem_cache *s, int forced_order) > * > * This is the case if we do RCU, have a constructor or > * destructor or are poisoning the objects. > + * > + * The assumption that s->offset >= s->inuse means free > + * pointer is outside of the object is used in the > + * freeptr_outside_object() function. If that is no > + * longer true, the function needs to be modified. > */ > s->offset = size; > size += sizeof(void *); > -- > 2.18.1 > > Acked-by: Rafael Aquini