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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 04C06C28EBD for ; Sun, 9 Jun 2019 12:16:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D7CE52070B for ; Sun, 9 Jun 2019 12:16:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728462AbfFIMQh (ORCPT ); Sun, 9 Jun 2019 08:16:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:52292 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728256AbfFIMQh (ORCPT ); Sun, 9 Jun 2019 08:16:37 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D3EA2AF41; Sun, 9 Jun 2019 12:16:34 +0000 (UTC) Subject: Re: [RFC PATCH] bcache: fix stack corruption by PRECEDING_KEY() To: Pierre JUHEN , linux-bcache@vger.kernel.org Cc: Rolf Fokkens , Nix , linux-block@vger.kernel.org References: <20190608102204.60126-1-colyli@suse.de> <3e18ec39-5357-9239-ac06-d81558bd0fd1@suse.de> From: Coly Li Openpgp: preference=signencrypt Organization: SUSE Labs Message-ID: <0b9bd5dd-33ff-0b8f-ab30-a23216cd872f@suse.de> Date: Sun, 9 Jun 2019 20:16:26 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2019/6/9 6:46 下午, Pierre JUHEN wrote: > Hi Coly, > > As Rolf and I said, the value of preceding_key_p in the stack cannot be > set to NULL by your code. > > The modified patch hereafter does what you expect (I think). > Oh, I understand now. Yes you are right, I made a mistake in previous patch. I will post an update version which uses "struct bkey **preceding_key_p" as parameter of preceding_key(). And I will add Reviewed-by: tag to you (Pierre and Rolf) in update version. Thanks for your review! Coly Li >   > > drivers/md/bcache/bset.c | 16 +++++++++++++--- > drivers/md/bcache/bset.h | 34 ++++++++++++++++++++-------------- > 2 files changed, 33 insertions(+), 17 deletions(-) > > diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c > index 8f07fa6e1739..9422f3f1c682 100644 > --- a/drivers/md/bcache/bset.c > +++ b/drivers/md/bcache/bset.c > @@ -887,12 +887,22 @@ unsigned int bch_btree_insert_key(struct > btree_keys *b, struct bkey *k, >      struct bset *i = bset_tree_last(b)->data; >      struct bkey *m, *prev = NULL; >      struct btree_iter iter; > +    struct bkey preceding_key_on_stack = ZERO_KEY; > +    struct bkey *preceding_key_p = &preceding_key_on_stack; >   >      BUG_ON(b->ops->is_extents && !KEY_SIZE(k)); >   > -    m = bch_btree_iter_init(b, &iter, b->ops->is_extents > -                ? PRECEDING_KEY(&START_KEY(k)) > -                : PRECEDING_KEY(k)); > +    /* > +     * If k has preceding key, preceding_key_p will be set to address > +     *  of k's preceding key; otherwise preceding_key_p will be set > +     * to NULL inside preceding_key(). > +     */ > +    if (b->ops->is_extents) > +        preceding_key_p = preceding_key(&START_KEY(k), preceding_key_p); > +    else > +        preceding_key_p = preceding_key(k, preceding_key_p); > + > +    m = bch_btree_iter_init(b, &iter, preceding_key_p); >   >      if (b->ops->insert_fixup(b, k, &iter, replace_key)) >          return status; > diff --git a/drivers/md/bcache/bset.h b/drivers/md/bcache/bset.h > index bac76aabca6d..6ab165dcb717 100644 > --- a/drivers/md/bcache/bset.h > +++ b/drivers/md/bcache/bset.h > @@ -434,20 +434,26 @@ static inline bool bch_cut_back(const struct bkey > *where, struct bkey *k) >      return __bch_cut_back(where, k); >  } >   > -#define PRECEDING_KEY(_k)                    \ > -({                                \ > -    struct bkey *_ret = NULL;                \ > -                                \ > -    if (KEY_INODE(_k) || KEY_OFFSET(_k)) {            \ > -        _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0);    \ > -                                \ > -        if (!_ret->low)                    \ > -            _ret->high--;                \ > -        _ret->low--;                    \ > -    }                            \ > -                                \ > -    _ret;                            \ > -}) > +/* > + * Pointer preceding_key_p points to a memory object to store preceding > + * key of k. If the preceding key does not exist, set preceding_key_p to > + * NULL. So the caller of preceding_key() needs to take care of memory > + * which preceding_key_p pointed to before calling preceding_key(). > + * Currently the only caller of preceding_key() is bch_btree_insert_key(), > + * and preceding_key_p points to an on-stack variable, so the memory > + * release is handled by stackframe itself. > + */ > +static inline  struct bkey *preceding_key(struct bkey *k, struct bkey > *preceding_key_p) > +{ > +    if (KEY_INODE(k) || KEY_OFFSET(k)) { > +        *preceding_key_p = KEY(KEY_INODE(k), KEY_OFFSET(k), 0); > +        if (!preceding_key_p->low) > +            preceding_key_p->high--; > +        preceding_key_p->low--; > +        return (preceding_key_p); > +    } else { > +        return(NULL); > +    } > +} >   >  static inline bool bch_ptr_invalid(struct btree_keys *b, const struct > bkey *k) >  { > > -- Coly Li