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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4CA03ECAAD8 for ; Thu, 22 Sep 2022 20:47:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230000AbiIVUrV (ORCPT ); Thu, 22 Sep 2022 16:47:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229578AbiIVUrS (ORCPT ); Thu, 22 Sep 2022 16:47:18 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0264410AB31 for ; Thu, 22 Sep 2022 13:47:16 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 30D5B21A1B; Thu, 22 Sep 2022 20:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1663879635; h=from:from:reply-to: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; bh=G91bghnzz5qsrAZ1KwKzy4Is49Fx+R+59WwLRAB/H7c=; b=LD5f5mRsPBBGv/unmS6PKW+8j11tQoCJyDUIk5V1s2vWTiFyabHvrtykwnhRBcbqBaTR+d di6/nPRJUx4b/EhRF1K/dzkLmo5Dx7PpP7tl9ZRbKqNz0K7m1h1fwozP3PEua41K74uaJB 8e+i8oYCm95dB7pVQ413LQLI4Kc2pIQ= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1663879635; h=from:from:reply-to: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; bh=G91bghnzz5qsrAZ1KwKzy4Is49Fx+R+59WwLRAB/H7c=; b=bqkZQTDBGGe6kA9+RxsH35mSaR2qMh34fY0Dbv/LZvMMd/n/OzSrhrllMdPYaaSfAK3Okt ezS9Mvx2iP6vmVBw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id EB6EA13AA5; Thu, 22 Sep 2022 20:47:14 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 44fJONLJLGO6IQAAMHmgww (envelope-from ); Thu, 22 Sep 2022 20:47:14 +0000 Message-ID: <719a7ea0-c152-af03-8f6c-7dda702d1863@suse.cz> Date: Thu, 22 Sep 2022 22:47:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH] mm/slub: clean up create_unique_id() Content-Language: en-US To: Chao Yu , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Hugh Dickins Cc: Chao Yu , Christophe JAILLET , Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220918092146.4060783-1-chao@kernel.org> From: Vlastimil Babka In-Reply-To: <20220918092146.4060783-1-chao@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/18/22 11:21, Chao Yu wrote: > From: Chao Yu > > As Christophe JAILLET suggested: > > In create_unique_id(), > > "looks that ID_STR_LENGTH could even be reduced to 32 or 16. > > The 2nd BUG_ON at the end of the function could certainly be just > removed as well or remplaced by a: > if (p > name + ID_STR_LENGTH - 1) { > kfree(name); > return -E; > } > " > > According to above suggestion, let's do below cleanups: > 1. reduce ID_STR_LENGTH to 32, as the buffer size should be enough; > 2. remove BUG_ON() and return error if check condition is true. I'd leave a WARN_ON there as we really don't expect this to happen, so if it does, we should be loud about it and not silently fail. > Link: https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@wanadoo.fr/ > Suggested-by: Christophe JAILLET > Fixes: 81819f0fc828 ("SLUB core") > Signed-off-by: Chao Yu > --- > mm/slub.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 5ba6db62a5ab..a045c1ca8772 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5883,7 +5883,7 @@ static inline struct kset *cache_kset(struct kmem_cache *s) > return slab_kset; > } > > -#define ID_STR_LENGTH 64 > +#define ID_STR_LENGTH 32 > > /* Create a unique string id for a slab cache: > * > @@ -5919,7 +5919,10 @@ static char *create_unique_id(struct kmem_cache *s) > *p++ = '-'; > p += sprintf(p, "%07u", s->size); Hm but sprintf() will happily overflow, so if we only detect that afterwards, it's kinda too late to gracefully fail. Should use snprintf() then? > - BUG_ON(p > name + ID_STR_LENGTH - 1); > + if (p > name + ID_STR_LENGTH - 1) { > + kfree(name); > + return ERR_PTR(-EINVAL); > + } > return name; > } >