* Qian Cai <quic_qiancai@xxxxxxxxxxx> [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. Cheers, Liam
