From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 17D916EB5C; Thu, 14 Mar 2024 11:24:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710415502; cv=none; b=GdI0bNDXks6SdbSHnKodZBBUHSDQNYN7c7E3HFmEfFbtLsi6OJHbOVGK486rO7fA9RYsLKdVFdO4+zJg63XseEfrA6vimPh6gDUO8I9pVbLB9hvUs6SQKiiA8QjRZXoYq54Ijg5F2o30MDUPMRfs3ZhkvQJsdmyHdXQy8U/QvQM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710415502; c=relaxed/simple; bh=dRotbT0kJtqO9wQLyoxla3srawYljMDh+1EQIZUfVDk=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=HUue4l/ayEv6OYflYejoI8tlywYs/7Zi1r6RNtR/OPCzvr/y50Zezw8CoSHKMcxELY6klQcp4pnAornjAMbLj+nzeXJhXoEJoqB6h2sV1DrGFafE8Br868uXaY7omV/AuZLOx/V9A4P5HnLBoukvgp8OnmWmE9Op/k8NCZmAfPA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.17]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4TwQ3f6tqGz1xqxw; Thu, 14 Mar 2024 19:23:10 +0800 (CST) Received: from dggpeml500021.china.huawei.com (unknown [7.185.36.21]) by mail.maildlp.com (Postfix) with ESMTPS id 5DAC41A0187; Thu, 14 Mar 2024 19:24:57 +0800 (CST) Received: from [10.174.177.174] (10.174.177.174) by dggpeml500021.china.huawei.com (7.185.36.21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Thu, 14 Mar 2024 19:24:56 +0800 Message-ID: <50f9333b-831a-8b4b-a6f2-ae79ab46a88b@huawei.com> Date: Thu, 14 Mar 2024 19:24:56 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH v2 4/9] ext4: fix slab-out-of-bounds in ext4_mb_find_good_group_avg_frag_lists() Content-Language: en-US To: Jan Kara CC: , , , , , , , , , , Baokun Li References: <20240227091148.178435-1-libaokun1@huawei.com> <20240227091148.178435-5-libaokun1@huawei.com> <20240314103056.rykwi2hhfm7v575a@quack3> From: Baokun Li In-Reply-To: <20240314103056.rykwi2hhfm7v575a@quack3> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500021.china.huawei.com (7.185.36.21) Hi Jan, On 2024/3/14 18:30, Jan Kara wrote: > On Tue 27-02-24 17:11:43, Baokun Li wrote: > > > At 4k block size, the length of the s_mb_avg_fragment_size list is 14, > but an oversized s_mb_group_prealloc is set, causing slab-out-of-bounds > to be triggered by an attempt to access an element at index 29. > > Add a new attr_id attr_clusters_in_group with values in the range > [0, sbi->s_clusters_per_group] and declare mb_group_prealloc as > that type to fix the issue. In addition avoid returning an order > from mb_avg_fragment_size_order() greater than MB_NUM_ORDERS(sb) > and reduce some useless loops. > > Fixes: 7e170922f06b ("ext4: Add allocation criteria 1.5 (CR1_5)") > CC: stable@vger.kernel.org > Signed-off-by: Baokun Li > Looks good. Just one nit below. Otherwise feel free to add: > > Reviewed-by: Jan Kara > >> --- >> fs/ext4/mballoc.c | 6 ++++++ >> fs/ext4/sysfs.c | 13 ++++++++++++- >> 2 files changed, 18 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c >> index 85a91a61b761..7ad089df2408 100644 >> --- a/fs/ext4/mballoc.c >> +++ b/fs/ext4/mballoc.c >> @@ -831,6 +831,8 @@ static int mb_avg_fragment_size_order(struct super_block *sb, ext4_grpblk_t len) >> return 0; >> if (order == MB_NUM_ORDERS(sb)) >> order--; >> + if (WARN_ON_ONCE(order > MB_NUM_ORDERS(sb))) >> + order = MB_NUM_ORDERS(sb) - 1; >> return order; >> } >> >> @@ -1057,6 +1059,10 @@ static void ext4_mb_choose_next_group_best_avail(struct ext4_allocation_context >> ac->ac_flags |= EXT4_MB_CR_BEST_AVAIL_LEN_OPTIMIZED; >> return; >> } >> + >> + /* Skip some unnecessary loops. */ >> + if (unlikely(i > MB_NUM_ORDERS(ac->ac_sb))) >> + i = MB_NUM_ORDERS(ac->ac_sb); > How can this possibly trigger now? MB_NUM_ORDERS is sb->s_blocksize_bits + > 2. 'i' is starting at fls(ac->ac_g_ex.fe_len) and ac_g_ex.fe_len shouldn't > be larger than clusters per group, hence fls() should be less than > sb->s_blocksize_bits? Am I missing something? And if yes, we should rather > make sure 'order' is never absurdly big? > > I suspect this code is defensive upto a point of being confusing :) > > Honza Yes, this is indeed defensive code! Only walk into this branch when WARN_ON_ONCE(order > MB_NUM_ORDERS(sb)) is triggered. As previously mentioned by ojaswin in the following link: "The reason for this is that otherwise when order is large eg 29, we would unnecessarily loop from i=29 to i=13 while always looking at the same avg_fragment_list[13]." Link：https://lore.kernel.org/lkml/ZdQ7FEA7KC4eAMpg@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com/ Thank you so much for the review! ღ( ´･ᴗ･` ) -- With Best Regards, Baokun Li .