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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.1 Subject: Re: [PATCH v2] mm/slub: clean up create_unique_id() Content-Language: en-US To: Chao Yu , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Hugh Dickins Cc: Chao Yu , Christophe JAILLET , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220925071207.13183-1-chao@kernel.org> From: Vlastimil Babka In-Reply-To: <20220925071207.13183-1-chao@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1664180563; h=from:from:sender:reply-to:subject:subject: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:dkim-signature; bh=e0ewHd4r4cN7IT1a+zjfxyxiaox5vNngvtrBQg4vrbI=; 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dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b="s4/b1hp8"; dmarc=none; spf=pass (imf21.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-HE-Tag: 1664180563-354401 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 9/25/22 09:12, 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. use WARN_ON instead of BUG_ON() and return error if check condition > is true; > 3. use snprintf instead of sprintf to avoid overflow. > > Link: https://lore.kernel.org/linux-mm/2025305d-16db-abdf-6cd3-1fb93371c2b4@wanadoo.fr/ > Fixes: 81819f0fc828 ("SLUB core") > Suggested-by: Christophe JAILLET > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > Signed-off-by: Chao Yu > --- > v2: > - add WARN_ON() instead of return error silently; > - use snprintf instead of sprintf to avoid overflow. > mm/slub.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 4b98dff9be8e..3d37a8a7b965 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -5890,7 +5890,7 @@ 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: > * > @@ -5924,9 +5924,13 @@ static char *create_unique_id(struct kmem_cache *s) > *p++ = 'A'; > if (p != name + 1) > *p++ = '-'; > - p += sprintf(p, "%07u", s->size); > + p += snprintf(p, ID_STR_LENGTH - 1 - (p - name), "%07u", s->size); I think we don't need "- 1" here as snprintf() says: @size: The size of the buffer, including the trailing null space > > - BUG_ON(p > name + ID_STR_LENGTH - 1); > + if (p > name + ID_STR_LENGTH - 1) { > + WARN_ON(1); This would be shorter: if (WARN_ON(p > name...)) > + kfree(name); > + return ERR_PTR(-EINVAL); > + } > return name; > } >