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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01878C433EF for ; Mon, 4 Oct 2021 13:35:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E0C52611C7 for ; Mon, 4 Oct 2021 13:35:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234052AbhJDNhl (ORCPT ); Mon, 4 Oct 2021 09:37:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:48650 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235019AbhJDNf3 (ORCPT ); Mon, 4 Oct 2021 09:35:29 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id A1CB563239; Mon, 4 Oct 2021 13:16:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1633353361; bh=9kAS1EdsWHXPEiGsFvpceYBJh9ghv41JBffYWz0WCcs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PHRXrLtmoq2/lrbHp4IHu1hdAMR1YSBs6+47Uf8hOYo6Y9qcpBzIfGTvseGK6DeN0 cRM8nFe9weJxdEnPaHoGZX/wfsNnDf1QW5rs2IQMDc57AxL7uMmM6sIDasJLAGjYMy kQcuflzHaPptLLMldxc0f78Pf/juuYE9JcmcunOo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , Rasmus Villemoes , Naresh Kamboju , Nathan Chancellor , Stephen Rothwell , Kees Cook , Linus Torvalds , Pavel Machek , Nick Desaulniers , Josef Bacik , Jens Axboe Subject: [PATCH 5.14 066/172] nbd: use shifts rather than multiplies Date: Mon, 4 Oct 2021 14:51:56 +0200 Message-Id: <20211004125047.122127830@linuxfoundation.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211004125044.945314266@linuxfoundation.org> References: <20211004125044.945314266@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Nick Desaulniers commit 41e76c6a3c83c85e849f10754b8632ea763d9be4 upstream. commit fad7cd3310db ("nbd: add the check to prevent overflow in __nbd_ioctl()") raised an issue from the fallback helpers added in commit f0907827a8a9 ("compiler.h: enable builtin overflow checkers and add fallback code") ERROR: modpost: "__divdi3" [drivers/block/nbd.ko] undefined! As Stephen Rothwell notes: The added check_mul_overflow() call is being passed 64 bit values. COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW is not set for this build (see include/linux/overflow.h). Specifically, the helpers for checking whether the results of a multiplication overflowed (__unsigned_mul_overflow, __signed_add_overflow) use the division operator when !COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW. This is problematic for 64b operands on 32b hosts. This was fixed upstream by commit 76ae847497bc ("Documentation: raise minimum supported version of GCC to 5.1") which is not suitable to be backported to stable. Further, __builtin_mul_overflow() would emit a libcall to a compiler-rt-only symbol when compiling with clang < 14 for 32b targets. ld.lld: error: undefined symbol: __mulodi4 In order to keep stable buildable with GCC 4.9 and clang < 14, modify struct nbd_config to instead track the number of bits of the block size; reconstructing the block size using runtime checked shifts that are not problematic for those compilers and in a ways that can be backported to stable. In nbd_set_size, we do validate that the value of blksize must be a power of two (POT) and is in the range of [512, PAGE_SIZE] (both inclusive). This does modify the debugfs interface. Cc: stable@vger.kernel.org Cc: Arnd Bergmann Cc: Rasmus Villemoes Link: https://github.com/ClangBuiltLinux/linux/issues/1438 Link: https://lore.kernel.org/all/20210909182525.372ee687@canb.auug.org.au/ Link: https://lore.kernel.org/stable/CAHk-=whiQBofgis_rkniz8GBP9wZtSZdcDEffgSLO62BUGV3gg@mail.gmail.com/ Reported-by: Naresh Kamboju Reported-by: Nathan Chancellor Reported-by: Stephen Rothwell Suggested-by: Kees Cook Suggested-by: Linus Torvalds Suggested-by: Pavel Machek Signed-off-by: Nick Desaulniers Reviewed-by: Josef Bacik Link: https://lore.kernel.org/r/20210920232533.4092046-1-ndesaulniers@google.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/block/nbd.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -97,13 +97,18 @@ struct nbd_config { atomic_t recv_threads; wait_queue_head_t recv_wq; - loff_t blksize; + unsigned int blksize_bits; loff_t bytesize; #if IS_ENABLED(CONFIG_DEBUG_FS) struct dentry *dbg_dir; #endif }; +static inline unsigned int nbd_blksize(struct nbd_config *config) +{ + return 1u << config->blksize_bits; +} + struct nbd_device { struct blk_mq_tag_set tag_set; @@ -147,7 +152,7 @@ static struct dentry *nbd_dbg_dir; #define NBD_MAGIC 0x68797548 -#define NBD_DEF_BLKSIZE 1024 +#define NBD_DEF_BLKSIZE_BITS 10 static unsigned int nbds_max = 16; static int max_part = 16; @@ -350,12 +355,12 @@ static int nbd_set_size(struct nbd_devic loff_t blksize) { if (!blksize) - blksize = NBD_DEF_BLKSIZE; + blksize = 1u << NBD_DEF_BLKSIZE_BITS; if (blksize < 512 || blksize > PAGE_SIZE || !is_power_of_2(blksize)) return -EINVAL; nbd->config->bytesize = bytesize; - nbd->config->blksize = blksize; + nbd->config->blksize_bits = __ffs(blksize); if (!nbd->task_recv) return 0; @@ -1370,7 +1375,7 @@ static int nbd_start_device(struct nbd_d args->index = i; queue_work(nbd->recv_workq, &args->work); } - return nbd_set_size(nbd, config->bytesize, config->blksize); + return nbd_set_size(nbd, config->bytesize, nbd_blksize(config)); } static int nbd_start_device_ioctl(struct nbd_device *nbd, struct block_device *bdev) @@ -1439,11 +1444,11 @@ static int __nbd_ioctl(struct block_devi case NBD_SET_BLKSIZE: return nbd_set_size(nbd, config->bytesize, arg); case NBD_SET_SIZE: - return nbd_set_size(nbd, arg, config->blksize); + return nbd_set_size(nbd, arg, nbd_blksize(config)); case NBD_SET_SIZE_BLOCKS: - if (check_mul_overflow((loff_t)arg, config->blksize, &bytesize)) + if (check_shl_overflow(arg, config->blksize_bits, &bytesize)) return -EINVAL; - return nbd_set_size(nbd, bytesize, config->blksize); + return nbd_set_size(nbd, bytesize, nbd_blksize(config)); case NBD_SET_TIMEOUT: nbd_set_cmd_timeout(nbd, arg); return 0; @@ -1509,7 +1514,7 @@ static struct nbd_config *nbd_alloc_conf atomic_set(&config->recv_threads, 0); init_waitqueue_head(&config->recv_wq); init_waitqueue_head(&config->conn_wait); - config->blksize = NBD_DEF_BLKSIZE; + config->blksize_bits = NBD_DEF_BLKSIZE_BITS; atomic_set(&config->live_connections, 0); try_module_get(THIS_MODULE); return config; @@ -1637,7 +1642,7 @@ static int nbd_dev_dbg_init(struct nbd_d debugfs_create_file("tasks", 0444, dir, nbd, &nbd_dbg_tasks_fops); debugfs_create_u64("size_bytes", 0444, dir, &config->bytesize); debugfs_create_u32("timeout", 0444, dir, &nbd->tag_set.timeout); - debugfs_create_u64("blocksize", 0444, dir, &config->blksize); + debugfs_create_u32("blocksize_bits", 0444, dir, &config->blksize_bits); debugfs_create_file("flags", 0444, dir, nbd, &nbd_dbg_flags_fops); return 0; @@ -1841,7 +1846,7 @@ nbd_device_policy[NBD_DEVICE_ATTR_MAX + static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd) { struct nbd_config *config = nbd->config; - u64 bsize = config->blksize; + u64 bsize = nbd_blksize(config); u64 bytes = config->bytesize; if (info->attrs[NBD_ATTR_SIZE_BYTES]) @@ -1850,7 +1855,7 @@ static int nbd_genl_size_set(struct genl if (info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]) bsize = nla_get_u64(info->attrs[NBD_ATTR_BLOCK_SIZE_BYTES]); - if (bytes != config->bytesize || bsize != config->blksize) + if (bytes != config->bytesize || bsize != nbd_blksize(config)) return nbd_set_size(nbd, bytes, bsize); return 0; }