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c4f9c701f9
It is reported that the following bug is triggered if the HDD is used as
swap device,
[ 5758.157556] BUG: kernel NULL pointer dereference, address: 0000000000000007
[ 5758.165331] #PF: supervisor write access in kernel mode
[ 5758.171161] #PF: error_code(0x0002) - not-present page
[ 5758.176894] PGD 0 P4D 0
[ 5758.179721] Oops: 0002 [#1] SMP PTI
[ 5758.183614] CPU: 10 PID: 316 Comm: kswapd1 Kdump: loaded Tainted: G S --------- --- 5.9.0-0.rc3.1.tst.el8.x86_64 #1
[ 5758.196717] Hardware name: Intel Corporation S2600CP/S2600CP, BIOS SE5C600.86B.02.01.0002.082220131453 08/22/2013
[ 5758.208176] RIP: 0010:split_swap_cluster+0x47/0x60
[ 5758.213522] Code: c1 e3 06 48 c1 eb 0f 48 8d 1c d8 48 89 df e8 d0 20 6a 00 80 63 07 fb 48 85 db 74 16 48 89 df c6 07 00 66 66 66 90 31 c0 5b c3 <80> 24 25 07 00 00 00 fb 31 c0 5b c3 b8 f0 ff ff ff 5b c3 66 0f 1f
[ 5758.234478] RSP: 0018:ffffb147442d7af0 EFLAGS: 00010246
[ 5758.240309] RAX: 0000000000000000 RBX: 000000000014b217 RCX: ffffb14779fd9000
[ 5758.248281] RDX: 000000000014b217 RSI: ffff9c52f2ab1400 RDI: 000000000014b217
[ 5758.256246] RBP: ffffe00c51168080 R08: ffffe00c5116fe08 R09: ffff9c52fffd3000
[ 5758.264208] R10: ffffe00c511537c8 R11: ffff9c52fffd3c90 R12: 0000000000000000
[ 5758.272172] R13: ffffe00c51170000 R14: ffffe00c51170000 R15: ffffe00c51168040
[ 5758.280134] FS: 0000000000000000(0000) GS:ffff9c52f2a80000(0000) knlGS:0000000000000000
[ 5758.289163] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 5758.295575] CR2: 0000000000000007 CR3: 0000000022a0e003 CR4: 00000000000606e0
[ 5758.303538] Call Trace:
[ 5758.306273] split_huge_page_to_list+0x88b/0x950
[ 5758.311433] deferred_split_scan+0x1ca/0x310
[ 5758.316202] do_shrink_slab+0x12c/0x2a0
[ 5758.320491] shrink_slab+0x20f/0x2c0
[ 5758.324482] shrink_node+0x240/0x6c0
[ 5758.328469] balance_pgdat+0x2d1/0x550
[ 5758.332652] kswapd+0x201/0x3c0
[ 5758.336157] ? finish_wait+0x80/0x80
[ 5758.340147] ? balance_pgdat+0x550/0x550
[ 5758.344525] kthread+0x114/0x130
[ 5758.348126] ? kthread_park+0x80/0x80
[ 5758.352214] ret_from_fork+0x22/0x30
[ 5758.356203] Modules linked in: fuse zram rfkill sunrpc intel_rapl_msr intel_rapl_common sb_edac x86_pkg_temp_thermal intel_powerclamp coretemp mgag200 iTCO_wdt crct10dif_pclmul iTCO_vendor_support drm_kms_helper crc32_pclmul ghash_clmulni_intel syscopyarea sysfillrect sysimgblt fb_sys_fops cec rapl joydev intel_cstate ipmi_si ipmi_devintf drm intel_uncore i2c_i801 ipmi_msghandler pcspkr lpc_ich mei_me i2c_smbus mei ioatdma ip_tables xfs libcrc32c sr_mod sd_mod cdrom t10_pi sg igb ahci libahci i2c_algo_bit crc32c_intel libata dca wmi dm_mirror dm_region_hash dm_log dm_mod
[ 5758.412673] CR2: 0000000000000007
[ 0.000000] Linux version 5.9.0-0.rc3.1.tst.el8.x86_64 (mockbuild@x86-vm-15.build.eng.bos.redhat.com) (gcc (GCC) 8.3.1 20191121 (Red Hat 8.3.1-5), GNU ld version 2.30-79.el8) #1 SMP Wed Sep 9 16:03:34 EDT 2020
After further digging it's found that the following race condition exists in the
original implementation,
CPU1 CPU2
---- ----
deferred_split_scan()
split_huge_page(page) /* page isn't compound head */
split_huge_page_to_list(page, NULL)
__split_huge_page(page, )
ClearPageCompound(head)
/* unlock all subpages except page (not head) */
add_to_swap(head) /* not THP */
get_swap_page(head)
add_to_swap_cache(head, )
SetPageSwapCache(head)
if PageSwapCache(head)
split_swap_cluster(/* swap entry of head */)
/* Deref sis->cluster_info: NULL accessing! */
So, in split_huge_page_to_list(), PageSwapCache() is called for the already
split and unlocked "head", which may be added to swap cache in another CPU. So
split_swap_cluster() may be called wrongly.
To fix the race, the call to split_swap_cluster() is moved to
__split_huge_page() before all subpages are unlocked. So that the
PageSwapCache() is stable.
Fixes:
|
||
|---|---|---|
| .. | ||
| kasan | ||
| backing-dev.c | ||
| balloon_compaction.c | ||
| cleancache.c | ||
| cma_debug.c | ||
| cma.c | ||
| cma.h | ||
| compaction.c | ||
| debug_page_ref.c | ||
| debug_vm_pgtable.c | ||
| debug.c | ||
| dmapool.c | ||
| early_ioremap.c | ||
| fadvise.c | ||
| failslab.c | ||
| filemap.c | ||
| frame_vector.c | ||
| frontswap.c | ||
| gup_benchmark.c | ||
| gup.c | ||
| highmem.c | ||
| hmm.c | ||
| huge_memory.c | ||
| hugetlb_cgroup.c | ||
| hugetlb.c | ||
| hwpoison-inject.c | ||
| init-mm.c | ||
| internal.h | ||
| interval_tree.c | ||
| ioremap.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| khugepaged.c | ||
| kmemleak.c | ||
| ksm.c | ||
| list_lru.c | ||
| maccess.c | ||
| madvise.c | ||
| Makefile | ||
| mapping_dirty_helpers.c | ||
| memblock.c | ||
| memcontrol.c | ||
| memfd.c | ||
| memory_hotplug.c | ||
| memory-failure.c | ||
| memory.c | ||
| mempolicy.c | ||
| mempool.c | ||
| memremap.c | ||
| memtest.c | ||
| migrate.c | ||
| mincore.c | ||
| mlock.c | ||
| mm_init.c | ||
| mmap.c | ||
| mmu_gather.c | ||
| mmu_notifier.c | ||
| mmzone.c | ||
| mprotect.c | ||
| mremap.c | ||
| msync.c | ||
| nommu.c | ||
| oom_kill.c | ||
| page_alloc.c | ||
| page_counter.c | ||
| page_ext.c | ||
| page_idle.c | ||
| page_io.c | ||
| page_isolation.c | ||
| page_owner.c | ||
| page_poison.c | ||
| page_reporting.c | ||
| page_reporting.h | ||
| page_vma_mapped.c | ||
| page-writeback.c | ||
| pagewalk.c | ||
| percpu-internal.h | ||
| percpu-km.c | ||
| percpu-stats.c | ||
| percpu-vm.c | ||
| percpu.c | ||
| pgalloc-track.h | ||
| pgtable-generic.c | ||
| process_vm_access.c | ||
| ptdump.c | ||
| readahead.c | ||
| rmap.c | ||
| rodata_test.c | ||
| shmem.c | ||
| shuffle.c | ||
| shuffle.h | ||
| slab_common.c | ||
| slab.c | ||
| slab.h | ||
| slob.c | ||
| slub.c | ||
| sparse-vmemmap.c | ||
| sparse.c | ||
| swap_cgroup.c | ||
| swap_slots.c | ||
| swap_state.c | ||
| swap.c | ||
| swapfile.c | ||
| truncate.c | ||
| usercopy.c | ||
| userfaultfd.c | ||
| util.c | ||
| vmacache.c | ||
| vmalloc.c | ||
| vmpressure.c | ||
| vmscan.c | ||
| vmstat.c | ||
| workingset.c | ||
| z3fold.c | ||
| zbud.c | ||
| zpool.c | ||
| zsmalloc.c | ||
| zswap.c | ||