From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f198.google.com (mail-it1-f198.google.com [209.85.166.198]) by kanga.kvack.org (Postfix) with ESMTP id 277606B0C10 for ; Fri, 16 Nov 2018 18:44:19 -0500 (EST) Received: by mail-it1-f198.google.com with SMTP id p78-v6so301989itb.1 for ; Fri, 16 Nov 2018 15:44:19 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id c188-v6sor38064120itc.35.2018.11.16.15.44.17 for (Google Transport Security); Fri, 16 Nov 2018 15:44:17 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20181113152941.cc328e48d5c0c2f366f5db83@linux-foundation.org> References: <20181109084353.GA5321@dhcp22.suse.cz> <20181113094305.GM15120@dhcp22.suse.cz> <20181113152941.cc328e48d5c0c2f366f5db83@linux-foundation.org> From: Dmitry Vyukov Date: Fri, 16 Nov 2018 15:43:56 -0800 Message-ID: Subject: Re: UBSAN: Undefined behaviour in mm/page_alloc.c Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , Kyungtae Kim , pavel.tatashin@microsoft.com, Vlastimil Babka , osalvador@suse.de, Mike Rapoport , aaron.lu@intel.com, Joonsoo Kim , alexander.h.duyck@linux.intel.com, Mel Gorman , lifeasageek@gmail.com, "Dae R. Jeong" , syzkaller , LKML , Linux-MM , Konstantin Khlebnikov On Tue, Nov 13, 2018 at 3:29 PM, Andrew Morton wrote: > 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. kmalloc won't warn about large allocations after "mm: don't warn about large allocations for slab": https://lkml.org/lkml/2018/9/27/1156 It will just return NULL. That was already the case for slub. > 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? > > -- > You received this message because you are subscribed to the Google Groups "syzkaller" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller+unsubscribe@googlegroups.com. > For more options, visit https://groups.google.com/d/optout.