linux-kernel - Re: [PATCH v6 00/71] Introducing the Maple Tree

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Message-ID: <20220225202334.bsw5t3retcchpn2e@revolver>
Date:   Fri, 25 Feb 2022 20:23:41 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Qian Cai <quic_qiancai@...cinc.com>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v6 00/71] Introducing the Maple Tree

* Liam Howlett <liam.howlett@...cle.com> [220225 14:09]:
> * Qian Cai <quic_qiancai@...cinc.com> [220224 22:49]:
> > On Tue, Feb 15, 2022 at 02:37:44PM +0000, Liam Howlett wrote:
> > > The maple tree is an RCU-safe range based B-tree designed to use modern
> > > processor cache efficiently.  There are a number of places in the kernel
> > > that a non-overlapping range-based tree would be beneficial, especially
> > > one with a simple interface.  The first user that is covered in this
> > > patch set is the vm_area_struct, where three data structures are
> > > replaced by the maple tree: the augmented rbtree, the vma cache, and the
> > > linked list of VMAs in the mm_struct.  The long term goal is to reduce
> > > or remove the mmap_sem contention.
> > > 
> > > The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf
> > > nodes.  With the increased branching factor, it is significantly shorter than
> > > the rbtree so it has fewer cache misses.  The removal of the linked list
> > > between subsequent entries also reduces the cache misses and the need to pull
> > > in the previous and next VMA during many tree alterations.
> > > 
> > > This patch is based on v5.17-rc4
> > > 
> > > git: https://github.com/oracle/linux-uek/tree/howlett/maple/20220214
> > 
> > Just a heads-up. I noticed an use-after-free in today's linux-next below. I
> > am running out of time to fully triage this, but I noticed this is the only
> > series (not sure which revision) heavily touched mm/mmap.c recently there.
> > 
> >  BUG: KASAN: use-after-free in move_vma.isra.0
> >  Read of size 8 at addr ffff0009ce752ac8 by task systemd-logind/1280
> > 
> >  CPU: 21 PID: 1280 Comm: systemd-logind Not tainted 5.17.0-rc5-next-20220223-dirty #242
> >  Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 1.6 06/28/2020
> >  Call trace:
> >   dump_backtrace
> >   show_stack
> >   dump_stack_lvl
> >   print_address_description.constprop.0
> >   kasan_report
> >   __asan_report_load8_noabort
> >   move_vma.isra.0
> >   move_vma at /usr/src/linux-next/mm/mremap.c:714
> >   __do_sys_mremap
> >   __arm64_sys_mremap
> >   invoke_syscall
> >   el0_svc_common.constprop.0
> >   do_el0_svc
> >   el0_svc
> >   el0t_64_sync_handler
> >   el0t_64_sync
> > 
> >  Allocated by task 1280:
> >   kasan_save_stack
> >   __kasan_slab_alloc
> >   slab_post_alloc_hook
> >   kmem_cache_alloc
> >   vm_area_alloc
> >   vm_area_alloc at /usr/src/linux-next/kernel/fork.c:455
> >   mmap_region
> >   mmap_region at /usr/src/linux-next/mm/mmap.c:2585
> >   do_mmap
> >   vm_mmap_pgoff
> >   ksys_mmap_pgoff
> >   __arm64_sys_mmap
> >   invoke_syscall
> >   el0_svc_common.constprop.0
> >   do_el0_svc
> >   el0_svc
> >   el0t_64_sync_handler
> >   el0t_64_sync
> > 
> >  Freed by task 1280:
> >   kasan_save_stack
> >   kasan_set_track
> >   kasan_set_free_info
> >   __kasan_slab_free
> >   kmem_cache_free
> >   vm_area_free
> >   remove_vma
> >   remove_vma at /usr/src/linux-next/mm/mmap.c:187
> >   do_mas_align_munmap.isra.0
> >   remove_mt at /usr/src/linux-next/mm/mmap.c:2176
> >   (inlined by) do_mas_align_munmap at /usr/src/linux-next/mm/mmap.c:2437
> >   do_mas_munmap
> >   do_mas_munmap at /usr/src/linux-next/mm/mmap.c:2483
> >   do_munmap
> >   move_vma.isra.0
> >   __do_sys_mremap
> >   __arm64_sys_mremap
> >   invoke_syscall
> >   el0_svc_common.constprop.0
> >   do_el0_svc
> >   el0_svc
> >   el0t_64_sync_handler
> >   el0t_64_sync
> > 
> >  The buggy address belongs to the object at ffff0009ce752aa8
> >   which belongs to the cache vm_area_struct of size 144
> >  The buggy address is located 32 bytes inside of
> >   144-byte region [ffff0009ce752aa8, ffff0009ce752b38)
> >  The buggy address belongs to the page:
> >  page:fffffc002739d400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa4e750
> >  head:fffffc002739d400 order:2 compound_mapcount:0 compound_pincount:0
> >  memcg:ffff0009ce456e01
> >  flags: 0xbfffc0000010200(slab|head|node=0|zone=2|lastcpupid=0xffff)
> >  raw: 0bfffc0000010200 fffffc002739f108 fffffc00273a3b08 ffff000800f53380
> >  raw: 0000000000000000 0000000000210021 00000001ffffffff ffff0009ce456e01
> >  page dumped because: kasan: bad access detected
> > 
> >  Memory state around the buggy address:
> >   ffff0009ce752980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >   ffff0009ce752a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> >  >ffff0009ce752a80: fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb fb
> >                                                ^
> >   ffff0009ce752b00: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
> >   ffff0009ce752b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> 
> Thank you for the report.  I will try to reproduce it with a kvm here.
> 

I just booted an arm64 VM with my build and kasan enabled with no issue.
Could you please send me your config file for the build?

Thanks,
Liam