From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) by kanga.kvack.org (Postfix) with ESMTP id 7C7E56B000D for ; Tue, 13 Nov 2018 18:29:46 -0500 (EST) Received: by mail-pl1-f198.google.com with SMTP id 94-v6so10717361pla.5 for ; Tue, 13 Nov 2018 15:29:46 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id t9si8444038plz.427.2018.11.13.15.29.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Nov 2018 15:29:45 -0800 (PST) Date: Tue, 13 Nov 2018 15:29:41 -0800 From: Andrew Morton Subject: Re: UBSAN: Undefined behaviour in mm/page_alloc.c Message-Id: <20181113152941.cc328e48d5c0c2f366f5db83@linux-foundation.org> In-Reply-To: <20181113094305.GM15120@dhcp22.suse.cz> References: <20181109084353.GA5321@dhcp22.suse.cz> <20181113094305.GM15120@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Kyungtae Kim , pavel.tatashin@microsoft.com, vbabka@suse.cz, osalvador@suse.de, rppt@linux.vnet.ibm.com, aaron.lu@intel.com, iamjoonsoo.kim@lge.com, alexander.h.duyck@linux.intel.com, mgorman@techsingularity.net, lifeasageek@gmail.com, threeearcat@gmail.com, syzkaller@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Konstantin Khlebnikov On Tue, 13 Nov 2018 10:43:05 +0100 Michal Hocko wrote: > From: Michal Hocko > Date: Fri, 9 Nov 2018 09:35:29 +0100 > Subject: [PATCH] mm, page_alloc: check for max order in hot path > > Konstantin has noticed that kvmalloc might trigger the following warning > [Thu Nov 1 08:43:56 2018] WARNING: CPU: 0 PID: 6676 at mm/vmstat.c:986 __fragmentation_index+0x54/0x60 um, wait... > [...] > [Thu Nov 1 08:43:56 2018] Call Trace: > [Thu Nov 1 08:43:56 2018] fragmentation_index+0x76/0x90 > [Thu Nov 1 08:43:56 2018] compaction_suitable+0x4f/0xf0 > [Thu Nov 1 08:43:56 2018] shrink_node+0x295/0x310 > [Thu Nov 1 08:43:56 2018] node_reclaim+0x205/0x250 > [Thu Nov 1 08:43:56 2018] get_page_from_freelist+0x649/0xad0 > [Thu Nov 1 08:43:56 2018] ? get_page_from_freelist+0x2d4/0xad0 > [Thu Nov 1 08:43:56 2018] ? release_sock+0x19/0x90 > [Thu Nov 1 08:43:56 2018] ? do_ipv6_setsockopt.isra.5+0x10da/0x1290 > [Thu Nov 1 08:43:56 2018] __alloc_pages_nodemask+0x12a/0x2a0 > [Thu Nov 1 08:43:56 2018] kmalloc_large_node+0x47/0x90 > [Thu Nov 1 08:43:56 2018] __kmalloc_node+0x22b/0x2e0 > [Thu Nov 1 08:43:56 2018] kvmalloc_node+0x3e/0x70 > [Thu Nov 1 08:43:56 2018] xt_alloc_table_info+0x3a/0x80 [x_tables] > [Thu Nov 1 08:43:56 2018] do_ip6t_set_ctl+0xcd/0x1c0 [ip6_tables] > [Thu Nov 1 08:43:56 2018] nf_setsockopt+0x44/0x60 > [Thu Nov 1 08:43:56 2018] SyS_setsockopt+0x6f/0xc0 > [Thu Nov 1 08:43:56 2018] do_syscall_64+0x67/0x120 > [Thu Nov 1 08:43:56 2018] entry_SYSCALL_64_after_hwframe+0x3d/0xa2 If kvalloc_node() is going to call kmalloc() without checking for a huge allocation request then surely it should set __GFP_NOWARN. And it shouldn't bother at all if size > KMALLOC_MAX_SIZE, surely? So something like --- a/mm/util.c~a +++ a/mm/util.c @@ -393,11 +393,16 @@ void *kvmalloc_node(size_t size, gfp_t f void *ret; /* - * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables) - * so the given set of flags has to be compatible. + * vmalloc uses GFP_KERNEL for some internal allocations (e.g page + * tables) so the given set of flags has to be compatible. */ - if ((flags & GFP_KERNEL) != GFP_KERNEL) + if ((flags & GFP_KERNEL) != GFP_KERNEL) { + if (size > KMALLOC_MAX_SIZE) + return NULL; + if (size > PAGE_SIZE) + flags |= __GFP_NOWARN; return kmalloc_node(size, flags, node); + } /* * We want to attempt a large physically contiguous block first because > the problem is that we only check for an out of bound order in the slow > path and the node reclaim might happen from the fast path already. This > is fixable by making sure that kvmalloc doesn't ever use kmalloc for > requests that are larger than KMALLOC_MAX_SIZE but this also shows that > the code is rather fragile. A recent UBSAN report just underlines that > by the following report > > UBSAN: Undefined behaviour in mm/page_alloc.c:3117:19 > shift exponent 51 is too large for 32-bit type 'int' > CPU: 0 PID: 6520 Comm: syz-executor1 Not tainted 4.19.0-rc2 #1 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xd2/0x148 lib/dump_stack.c:113 > ubsan_epilogue+0x12/0x94 lib/ubsan.c:159 > __ubsan_handle_shift_out_of_bounds+0x2b6/0x30b lib/ubsan.c:425 > __zone_watermark_ok+0x2c7/0x400 mm/page_alloc.c:3117 > zone_watermark_fast mm/page_alloc.c:3216 [inline] > get_page_from_freelist+0xc49/0x44c0 mm/page_alloc.c:3300 > __alloc_pages_nodemask+0x21e/0x640 mm/page_alloc.c:4370 > alloc_pages_current+0xcc/0x210 mm/mempolicy.c:2093 > alloc_pages include/linux/gfp.h:509 [inline] > __get_free_pages+0x12/0x60 mm/page_alloc.c:4414 > dma_mem_alloc+0x36/0x50 arch/x86/include/asm/floppy.h:156 > raw_cmd_copyin drivers/block/floppy.c:3159 [inline] > raw_cmd_ioctl drivers/block/floppy.c:3206 [inline] > fd_locked_ioctl+0xa00/0x2c10 drivers/block/floppy.c:3544 > fd_ioctl+0x40/0x60 drivers/block/floppy.c:3571 > __blkdev_driver_ioctl block/ioctl.c:303 [inline] > blkdev_ioctl+0xb3c/0x1a30 block/ioctl.c:601 > block_ioctl+0x105/0x150 fs/block_dev.c:1883 > vfs_ioctl fs/ioctl.c:46 [inline] > do_vfs_ioctl+0x1c0/0x1150 fs/ioctl.c:687 > ksys_ioctl+0x9e/0xb0 fs/ioctl.c:702 > __do_sys_ioctl fs/ioctl.c:709 [inline] > __se_sys_ioctl fs/ioctl.c:707 [inline] > __x64_sys_ioctl+0x7e/0xc0 fs/ioctl.c:707 > do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290 > entry_SYSCALL_64_after_hwframe+0x49/0xbe And we could fix this in the floppy driver. > Note that this is not a kvmalloc path. It is just that the fast path > really depends on having sanitzed order as well. Therefore move the > order check to the fast path. But do we really need to do this? Are there any other known potential callsites?