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 AE517C433EF for ; Sun, 3 Oct 2021 14:19:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C2AE619F7 for ; Sun, 3 Oct 2021 14:19:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230428AbhJCOUs (ORCPT ); Sun, 3 Oct 2021 10:20:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:53188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230482AbhJCOUs (ORCPT ); Sun, 3 Oct 2021 10:20:48 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8A88461B00; Sun, 3 Oct 2021 14:19:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1633270741; bh=RgfHgJSpLPf8WAC3OnelpG1Dd6jCbEBAic26hofEp8c=; h=Subject:To:Cc:From:Date:From; b=BzAeKnLufv1SWfn1mgEqsq6R0rHczdkj/3NayY6T/74tr1QnWesPyFfhhQEUSUlW0 H7pRsuwhiTaRJNFwg7mMQrsDcboURnycI8iQGOLC7eJFOp14YxPIV9OMkiW+qoTmDS BZRPNUf0cmxgic8kZugvaVdffVes+rAMM8mR5BqM= Subject: FAILED: patch "[PATCH] nbd: use shifts rather than multiplies" failed to apply to 5.10-stable tree To: ndesaulniers@google.com, arnd@kernel.org, axboe@kernel.dk, josef@toxicpanda.com, keescook@chromium.org, linux@rasmusvillemoes.dk, naresh.kamboju@linaro.org, nathan@kernel.org, pavel@ucw.cz, sfr@canb.auug.org.au, torvalds@linux-foundation.org Cc: From: Date: Sun, 03 Oct 2021 16:18:58 +0200 Message-ID: <163327073885127@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 41e76c6a3c83c85e849f10754b8632ea763d9be4 Mon Sep 17 00:00:00 2001 From: Nick Desaulniers Date: Mon, 20 Sep 2021 16:25:33 -0700 Subject: [PATCH] nbd: use shifts rather than multiplies 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 diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 5170a630778d..1183f7872b71 100644 --- 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; @@ -146,7 +151,7 @@ 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; @@ -317,12 +322,12 @@ static int nbd_set_size(struct nbd_device *nbd, loff_t bytesize, 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; @@ -1337,7 +1342,7 @@ static int nbd_start_device(struct nbd_device *nbd) 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) @@ -1406,11 +1411,11 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd, 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; @@ -1476,7 +1481,7 @@ static struct nbd_config *nbd_alloc_config(void) 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; @@ -1604,7 +1609,7 @@ static int nbd_dev_dbg_init(struct nbd_device *nbd) 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; @@ -1826,7 +1831,7 @@ nbd_device_policy[NBD_DEVICE_ATTR_MAX + 1] = { 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]) @@ -1835,7 +1840,7 @@ static int nbd_genl_size_set(struct genl_info *info, struct nbd_device *nbd) 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; }