From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) (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 7EFD96AAD for ; Thu, 14 Nov 2024 02:47:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.32 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731552469; cv=none; b=D9rSXCHdZPGKJ8ciSsyA1i4lYGgH/epWIZ4TLgtCN5jbKdBK6ggzeR4FiKkNJCr0rX0Rg52jXFLbCTRZPz0OnrEJv0mkE4RpM+LWqSPq50PHkLuK3So3NBhk84dPn+dGrogb2hY8Kt2+r7PtJ1U3msirDUqacNqetwaN4G4bdII= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731552469; c=relaxed/simple; bh=UXVNszelyeb3iVqgor+oDRpxrv4n1d0NR/9X78xSBXE=; h=Subject:To:CC:References:From:Message-ID:Date:MIME-Version: In-Reply-To:Content-Type; b=P/Eb+PIqs4Oo2oKIKHkRpyeHtVnTGEqbDE+Wu2/a50N+chGXmNjAolJ2ehi9b1x4BmFNQYq3N18BW4l86wAgis6qnZkgIsPE0G6d+Xu3UabRQQ6Afv4jwo+qe7HFiAo42RWzqmhTM3wjJFgPFCgSrl3frsXwYwfa/bDyimT6iiQ= 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=45.249.212.32 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 szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Xpl2243dKz1yqBC; Thu, 14 Nov 2024 10:47:54 +0800 (CST) Received: from kwepemf500004.china.huawei.com (unknown [7.202.181.242]) by mail.maildlp.com (Postfix) with ESMTPS id DDD341A0188; Thu, 14 Nov 2024 10:47:42 +0800 (CST) Received: from [10.67.110.237] (10.67.110.237) by kwepemf500004.china.huawei.com (7.202.181.242) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Thu, 14 Nov 2024 10:47:42 +0800 Subject: Re: [PATCH] topology: Keep the cpumask unchanged when printing cpumap To: Greg KH CC: , , , , References: <20241113165900.78095-1-lihuafei1@huawei.com> <2024111347-buggy-cranium-61c3@gregkh> From: Li Huafei Message-ID: <359b85aa-714f-f3cb-7096-28296dc2ea72@huawei.com> Date: Thu, 14 Nov 2024 10:47:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <2024111347-buggy-cranium-61c3@gregkh> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemf500004.china.huawei.com (7.202.181.242) On 2024/11/13 21:50, Greg KH wrote: > On Thu, Nov 14, 2024 at 12:59:00AM +0800, Li Huafei wrote: >> During fuzz testing, the following warning was discovered: >> >> different return values (15 and 11) from vsnprintf("%*pbl >> ", ...) >> >> test:keyward is WARNING in kvasprintf >> WARNING: CPU: 55 PID: 1168477 at lib/kasprintf.c:30 kvasprintf+0x121/0x130 >> Call Trace: >> kvasprintf+0x121/0x130 >> kasprintf+0xa6/0xe0 >> bitmap_print_to_buf+0x89/0x100 >> core_siblings_list_read+0x7e/0xb0 >> kernfs_file_read_iter+0x15b/0x270 >> new_sync_read+0x153/0x260 >> vfs_read+0x215/0x290 >> ksys_read+0xb9/0x160 >> do_syscall_64+0x56/0x100 >> entry_SYSCALL_64_after_hwframe+0x78/0xe2 > > What is happening when this fuzzing is going on? Removing/adding cpus? > Yes, logs of CPU offline also appeared before the warning. >> The call trace shows that kvasprintf() reported this warning during the >> printing of core_siblings_list. kvasprintf() has several steps: >> >> (1) First, calculate the length of the resulting formatted string. >> >> (2) Allocate a buffer based on the returned length. >> >> (3) Then, perform the actual string formatting. >> >> (4) Check whether the lengths of the formatted strings returned in >> steps (1) and (2) are consistent. >> >> If the core_cpumask is modified between steps (1) and (3), the lengths >> obtained in these two steps may not match. Indeed our test includes cpu >> hotplugging, which should modify core_cpumask while printing. > > Ah, yes. Good catch. > >> To fix this issue, cache the cpumask into a temporary variable before >> calling cpumap_print_{list, cpumask}_to_buf(), to keep it unchanged >> during the printing process. > > Nice, but: > >> >> Fixes: bb9ec13d156e ("topology: use bin_attribute to break the size limitation of cpumap ABI") > > No cc: stable? Thanks for the reminder, v2 will be cc'd to stable. > >> Signed-off-by: Li Huafei >> --- >> drivers/base/topology.c | 24 ++++++++++++++++++++---- >> 1 file changed, 20 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/base/topology.c b/drivers/base/topology.c >> index 89f98be5c5b9..70dbd7ef038d 100644 >> --- a/drivers/base/topology.c >> +++ b/drivers/base/topology.c >> @@ -27,9 +27,17 @@ static ssize_t name##_read(struct file *file, struct kobject *kobj, \ >> loff_t off, size_t count) \ >> { \ >> struct device *dev = kobj_to_dev(kobj); \ >> + cpumask_var_t mask; \ >> + ssize_t n; \ >> \ >> - return cpumap_print_bitmask_to_buf(buf, topology_##mask(dev->id), \ >> - off, count); \ >> + if (!alloc_cpumask_var(&mask, GFP_KERNEL)) \ >> + return 0; \ > > If this fails, return the error please. Don't return a size of 0, which > will just confuse userspace as to why the read succeeded yet did not > return any data? > Okay, v2 will change to return -ENOMEM, and the same applies to the following places. Thanks, Huafei >> + \ >> + cpumask_copy(mask, topology_##mask(dev->id)); \ >> + n = cpumap_print_bitmask_to_buf(buf, mask, off, count); \ >> + free_cpumask_var(mask); \ >> + \ >> + return n; \ >> } \ >> \ >> static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \ >> @@ -37,9 +45,17 @@ static ssize_t name##_list_read(struct file *file, struct kobject *kobj, \ >> loff_t off, size_t count) \ >> { \ >> struct device *dev = kobj_to_dev(kobj); \ >> + cpumask_var_t mask; \ >> + ssize_t n; \ >> + \ >> + if (!alloc_cpumask_var(&mask, GFP_KERNEL)) \ >> + return 0; \ > > Same here, please return the error. > > thanks, > > greg k-h > . >