Hi, Sorry for late reply. I found a problem in the swap readahead code. Can you help to check whether it can fix this? Best Regards, Huang, Ying ________________________________________ From: Qian Cai [cai@lca.pw] Sent: Tuesday, June 16, 2020 9:13 AM To: Huang, Ying Cc: Linux-MM; LKML; Minchan Kim; Hugh Dickins; Andrew Morton Subject: Re: linux-next: not-present page at swap_vma_readahead() On Wed, Apr 15, 2020 at 10:01:53AM +0800, Huang, Ying wrote: > Qian Cai writes: > > >> On Apr 14, 2020, at 10:32 AM, Qian Cai wrote: > >> > >> Fuzzers are unhappy. Thoughts? > > > > This is rather to reproduce. All the traces so far are from copy_from_user() to trigger a page fault, > > and then it dereferences a bad pte in swap_vma_readahead(), > > > > for (i = 0, pte = ra_info.ptes; i < ra_info.nr_pte; > > i++, pte++) { > > pentry = *pte; <— crashed here. > > if (pte_none(pentry)) > > Is it possible to bisect this? > > Because the crash point is identified, it may be helpful to collect and > analyze the status of the faulting page table and readahead ptes. But I > am not familiar with the ARM64 architecture. So I cannot help much > here. Ying, looks like the bug is still there today which manifests itself into a different form. Looking at the logs, I believe it was involved with swapoff(). Any other thought? I still have not found time to bisect this yet. [ 785.477183][ T8727] BUG: KASAN: slab-out-of-bounds in swapin_readahead+0x7b8/0xbc0 swap_vma_readahead at mm/swap_state.c:759 (inlined by) swapin_readahead at mm/swap_state.c:803 [ 785.484752][ T8727] Read of size 8 at addr ffff00886ecaffe8 by task trinity-c35/8727 [ 785.492488][ T8727] [ 785.494675][ T8727] CPU: 35 PID: 8727 Comm: trinity-c35 Not tainted 5.7.0-next-20200610 #3 [ 785.502942][ T8727] Hardware name: HPE Apollo 70 /C01_APACHE_MB , BIOS L50_5.13_1.11 06/18/2019 [ 785.513387][ T8727] Call trace: [ 785.516538][ T8727] dump_backtrace+0x0/0x398 [ 785.520891][ T8727] show_stack+0x14/0x20 [ 785.524900][ T8727] dump_stack+0x140/0x1b8 [ 785.529087][ T8727] print_address_description.isra.12+0x54/0x4a8 [ 785.535185][ T8727] kasan_report+0x134/0x1b8 [ 785.539545][ T8727] __asan_report_load8_noabort+0x2c/0x50 [ 785.545036][ T8727] swapin_readahead+0x7b8/0xbc0 [ 785.549745][ T8727] do_swap_page+0xb1c/0x19a0 [ 785.554195][ T8727] handle_mm_fault+0xf10/0x2b30 [ 785.558905][ T8727] do_page_fault+0x230/0x908 [ 785.563354][ T8727] do_translation_fault+0xe0/0x108 [ 785.568323][ T8727] do_mem_abort+0x64/0x180 [ 785.572597][ T8727] el1_sync_handler+0x188/0x1b8 [ 785.577305][ T8727] el1_sync+0x7c/0x100 [ 785.581232][ T8727] __arch_copy_to_user+0xc4/0x158 [ 785.586115][ T8727] __arm64_sys_sysinfo+0x2c/0xd0 [ 785.590912][ T8727] do_el0_svc+0x124/0x220 [ 785.595100][ T8727] el0_sync_handler+0x260/0x408 [ 785.599807][ T8727] el0_sync+0x140/0x180 [ 785.603818][ T8727] [ 785.606007][ T8727] Allocated by task 8673: [ 785.610193][ T8727] save_stack+0x24/0x50 [ 785.614208][ T8727] __kasan_kmalloc.isra.13+0xc4/0xe0 [ 785.619350][ T8727] kasan_slab_alloc+0x14/0x20 [ 785.623885][ T8727] slab_post_alloc_hook+0x50/0xa8 [ 785.628769][ T8727] kmem_cache_alloc+0x18c/0x438 [ 785.633479][ T8727] create_object+0x58/0x960 [ 785.637844][ T8727] kmemleak_alloc+0x2c/0x38 [ 785.642205][ T8727] slab_post_alloc_hook+0x70/0xa8 [ 785.647089][ T8727] kmem_cache_alloc_trace+0x178/0x308 [ 785.652322][ T8727] refill_pi_state_cache.part.10+0x3c/0x1a8 [ 785.658073][ T8727] futex_lock_pi+0x404/0x5e0 [ 785.662519][ T8727] do_futex+0x790/0x1448 [ 785.666618][ T8727] __arm64_sys_futex+0x204/0x588 [ 785.671411][ T8727] do_el0_svc+0x124/0x220 [ 785.675603][ T8727] el0_sync_handler+0x260/0x408 [ 785.680312][ T8727] el0_sync+0x140/0x180 [ 785.684322][ T8727] [ 785.686510][ T8727] Freed by task 0: [ 785.690088][ T8727] save_stack+0x24/0x50 [ 785.694104][ T8727] __kasan_slab_free+0x124/0x198 [ 785.698899][ T8727] kasan_slab_free+0x10/0x18 [ 785.703340][ T8727] slab_free_freelist_hook+0x110/0x298 [ 785.708648][ T8727] kmem_cache_free+0xc8/0x3e0 [ 785.713175][ T8727] free_object_rcu+0x1e0/0x3b8 [ 785.717796][ T8727] rcu_core+0x8bc/0xf40 [ 785.721810][ T8727] rcu_core_si+0xc/0x18 [ 785.725825][ T8727] efi_header_end+0x2d8/0x1204 [ 785.730442][ T8727] [ 785.732625][ T8727] The buggy address belongs to the object at ffff00886ecafd28 [ 785.732625][ T8727] which belongs to the cache kmemleak_object of size 368 [ 785.746875][ T8727] The buggy address is located 336 bytes to the right of [ 785.746875][ T8727] 368-byte region [ffff00886ecafd28, ffff00886ecafe98) [ 785.760519][ T8727] The buggy address belongs to the page: [ 785.766009][ T8727] page:ffffffe021fbb280 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff00886ecaa8c8 [ 785.776268][ T8727] flags: 0x7ffff800000200(slab) [ 785.780971][ T8727] raw: 007ffff800000200 ffffffe0222c12c8 ffffffe0223a1488 ffff000000323080 [ 785.789410][ T8727] raw: ffff00886ecaa8c8 00000000005b001d 00000001ffffffff 0000000000000000 [ 785.797849][ T8727] page dumped because: kasan: bad access85.811794][ T87270886ecaff00: fc fc fc fc fc fc ^ [ 785.842727] ffff00886ecb0080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 785.858703][ T8727] ================================================================== [ 785.866621][ T8727] Disabling lock debugging due to kernel taint [ 785.872714][ T8727] get_swap_device: Bad swap file entry 58025a5a5a5a5a5a [ 785.879523][ T8727] get_swap_device: Bad swap file entry 58025a5a5a5a5a5a [ 785.886322][ T8727] get_swap_device: Bad swap file entry 58025a5a5a5a5a5a