linux/mm
David Hildenbrand 0e678153f5 mm/hugetlb: fix PTE marker handling in hugetlb_change_protection()
Patch series "mm/hugetlb: uffd-wp fixes for hugetlb_change_protection()".

Playing with virtio-mem and background snapshots (using uffd-wp) on
hugetlb in QEMU, I managed to trigger a VM_BUG_ON().  Looking into the
details, hugetlb_change_protection() seems to not handle uffd-wp correctly
in all cases.

Patch #1 fixes my test case.  I don't have reproducers for patch #2, as it
requires running into migration entries.

I did not yet check in detail yet if !hugetlb code requires similar care.


This patch (of 2):

There are two problematic cases when stumbling over a PTE marker in
hugetlb_change_protection():

(1) We protect an uffd-wp PTE marker a second time using uffd-wp: we will
    end up in the "!huge_pte_none(pte)" case and mess up the PTE marker.

(2) We unprotect a uffd-wp PTE marker: we will similarly end up in the
    "!huge_pte_none(pte)" case even though we cleared the PTE, because
    the "pte" variable is stale. We'll mess up the PTE marker.

For example, if we later stumble over such a "wrongly modified" PTE marker,
we'll treat it like a present PTE that maps some garbage page.

This can, for example, be triggered by mapping a memfd backed by huge
pages, registering uffd-wp, uffd-wp'ing an unmapped page and (a)
uffd-wp'ing it a second time; or (b) uffd-unprotecting it; or (c)
unregistering uffd-wp. Then, ff we trigger fallocate(FALLOC_FL_PUNCH_HOLE)
on that file range, we will run into a VM_BUG_ON:

[  195.039560] page:00000000ba1f2987 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x0
[  195.039565] flags: 0x7ffffc0001000(reserved|node=0|zone=0|lastcpupid=0x1fffff)
[  195.039568] raw: 0007ffffc0001000 ffffe742c0000008 ffffe742c0000008 0000000000000000
[  195.039569] raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
[  195.039569] page dumped because: VM_BUG_ON_PAGE(compound && !PageHead(page))
[  195.039573] ------------[ cut here ]------------
[  195.039574] kernel BUG at mm/rmap.c:1346!
[  195.039579] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
[  195.039581] CPU: 7 PID: 4777 Comm: qemu-system-x86 Not tainted 6.0.12-200.fc36.x86_64 #1
[  195.039583] Hardware name: LENOVO 20WNS1F81N/20WNS1F81N, BIOS N35ET50W (1.50 ) 09/15/2022
[  195.039584] RIP: 0010:page_remove_rmap+0x45b/0x550
[  195.039588] Code: [...]
[  195.039589] RSP: 0018:ffffbc03c3633ba8 EFLAGS: 00010292
[  195.039591] RAX: 0000000000000040 RBX: ffffe742c0000000 RCX: 0000000000000000
[  195.039592] RDX: 0000000000000002 RSI: ffffffff8e7aac1a RDI: 00000000ffffffff
[  195.039592] RBP: 0000000000000001 R08: 0000000000000000 R09: ffffbc03c3633a08
[  195.039593] R10: 0000000000000003 R11: ffffffff8f146328 R12: ffff9b04c42754b0
[  195.039594] R13: ffffffff8fcc6328 R14: ffffbc03c3633c80 R15: ffff9b0484ab9100
[  195.039595] FS:  00007fc7aaf68640(0000) GS:ffff9b0bbf7c0000(0000) knlGS:0000000000000000
[  195.039596] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  195.039597] CR2: 000055d402c49110 CR3: 0000000159392003 CR4: 0000000000772ee0
[  195.039598] PKRU: 55555554
[  195.039599] Call Trace:
[  195.039600]  <TASK>
[  195.039602]  __unmap_hugepage_range+0x33b/0x7d0
[  195.039605]  unmap_hugepage_range+0x55/0x70
[  195.039608]  hugetlb_vmdelete_list+0x77/0xa0
[  195.039611]  hugetlbfs_fallocate+0x410/0x550
[  195.039612]  ? _raw_spin_unlock_irqrestore+0x23/0x40
[  195.039616]  vfs_fallocate+0x12e/0x360
[  195.039618]  __x64_sys_fallocate+0x40/0x70
[  195.039620]  do_syscall_64+0x58/0x80
[  195.039623]  ? syscall_exit_to_user_mode+0x17/0x40
[  195.039624]  ? do_syscall_64+0x67/0x80
[  195.039626]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[  195.039628] RIP: 0033:0x7fc7b590651f
[  195.039653] Code: [...]
[  195.039654] RSP: 002b:00007fc7aaf66e70 EFLAGS: 00000293 ORIG_RAX: 000000000000011d
[  195.039655] RAX: ffffffffffffffda RBX: 0000558ef4b7f370 RCX: 00007fc7b590651f
[  195.039656] RDX: 0000000018000000 RSI: 0000000000000003 RDI: 000000000000000c
[  195.039657] RBP: 0000000008000000 R08: 0000000000000000 R09: 0000000000000073
[  195.039658] R10: 0000000008000000 R11: 0000000000000293 R12: 0000000018000000
[  195.039658] R13: 00007fb8bbe00000 R14: 000000000000000c R15: 0000000000001000
[  195.039661]  </TASK>

Fix it by not going into the "!huge_pte_none(pte)" case if we stumble over
an exclusive marker.  spin_unlock() + continue would get the job done.

However, instead, make it clearer that there are no fall-through
statements: we process each case (hwpoison, migration, marker, !none,
none) and then unlock the page table to continue with the next PTE.  Let's
avoid "continue" statements and use a single spin_unlock() at the end.

Link: https://lkml.kernel.org/r/20221222205511.675832-1-david@redhat.com
Link: https://lkml.kernel.org/r/20221222205511.675832-2-david@redhat.com
Fixes: 60dfaad65a ("mm/hugetlb: allow uffd wr-protect none ptes")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-01-11 16:14:19 -08:00
..
damon mm/damon: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
kasan hardening updates for v6.2-rc1 2022-12-14 12:20:00 -08:00
kfence hardening updates for v6.2-rc1 2022-12-14 12:20:00 -08:00
kmsan kmsan: export kmsan_handle_urb 2022-12-21 14:31:52 -08:00
backing-dev.c mm: add /sys/class/bdi/<bdi>/min_ratio_fine knob 2022-11-30 15:59:06 -08:00
balloon_compaction.c mm: Convert all PageMovable users to movable_operations 2022-08-02 12:34:03 -04:00
bootmem_info.c bootmem: remove the vmemmap pages from kmemleak in put_page_bootmem 2022-08-28 14:02:45 -07:00
cma_debug.c mm/cma_debug: show complete cma name in debugfs directories 2022-09-11 20:25:50 -07:00
cma_sysfs.c
cma.c Revert "mm/cma.c: remove redundant cma_mutex lock" 2022-05-13 15:11:26 -07:00
cma.h
compaction.c mm, compaction: fix fast_isolate_around() to stay within boundaries 2022-11-30 15:59:07 -08:00
debug_page_ref.c
debug_vm_pgtable.c mm: remove unused savedwrite infrastructure 2022-11-30 15:58:49 -08:00
debug.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
dmapool.c
early_ioremap.c
fadvise.c mm/fadvise: use LLONG_MAX instead of -1 for eof 2022-12-11 18:12:11 -08:00
failslab.c mm: fix unexpected changes to {failslab|fail_page_alloc}.attr 2022-11-22 18:50:44 -08:00
filemap.c filemap: convert replace_page_cache_page() to replace_page_cache_folio() 2022-12-11 18:12:12 -08:00
folio-compat.c folio-compat: remove lru_cache_add() 2022-12-11 18:12:13 -08:00
frontswap.c frontswap: don't call ->init if no ops are registered 2022-09-26 12:14:34 -07:00
gup_test.c mm/gup_test: free memory allocated via kvcalloc() using kvfree() 2022-12-15 16:37:48 -08:00
gup_test.h mm/gup_test: start/stop/read functionality for PIN LONGTERM test 2022-11-08 17:37:15 -08:00
gup.c New Feature: 2022-12-17 14:06:53 -06:00
highmem.c highmem: fix kmap_to_page() for kmap_local_page() addresses 2022-10-12 18:51:51 -07:00
hmm.c mm: Remove pointless barrier() after pmdp_get_lockless() 2022-12-15 10:37:27 -08:00
huge_memory.c ARM64: 2022-12-15 11:12:21 -08:00
hugetlb_cgroup.c mm/hugeltb_cgroup: convert hugetlb_cgroup_commit_charge*() to folios 2022-11-30 15:58:43 -08:00
hugetlb_vmemmap.c mm/hugetlb_vmemmap: remap head page to newly allocated page 2022-11-30 15:58:47 -08:00
hugetlb_vmemmap.h mm: hugetlb_vmemmap: improve hugetlb_vmemmap code readability 2022-08-08 18:06:43 -07:00
hugetlb.c mm/hugetlb: fix PTE marker handling in hugetlb_change_protection() 2023-01-11 16:14:19 -08:00
hwpoison-inject.c mm/hwpoison: add __init/__exit annotations to module init/exit funcs 2022-10-03 14:03:05 -07:00
init-mm.c mm: remove rb tree. 2022-09-26 19:46:16 -07:00
internal.h mm/hwpoison: introduce per-memory_block hwpoison counter 2022-11-08 17:37:22 -08:00
interval_tree.c
io-mapping.c
ioremap.c mm: ioremap: Add ioremap/iounmap_allowed() 2022-06-27 12:22:31 +01:00
Kconfig New Feature: 2022-12-17 14:06:53 -06:00
Kconfig.debug mm, slub: add CONFIG_SLUB_TINY 2022-11-27 23:38:02 +01:00
khugepaged.c New Feature: 2022-12-17 14:06:53 -06:00
kmemleak.c mm/kmemleak: use %pK to display kernel pointers in backtrace 2022-12-15 16:37:49 -08:00
ksm.c mm/ksm: convert break_ksm() to use walk_page_range_vma() 2022-12-11 18:12:09 -08:00
list_lru.c mm: kmem: make mem_cgroup_from_obj() vmalloc()-safe 2022-06-16 19:48:31 -07:00
maccess.c maccess: Fix writing offset in case of fault in strncpy_from_kernel_nofault() 2022-11-11 11:44:46 -08:00
madvise.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
Makefile mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol 2022-10-03 14:03:36 -07:00
mapping_dirty_helpers.c mm: Rename pmd_read_atomic() 2022-12-15 10:37:27 -08:00
memblock.c memblock: Fix doc for memblock_phys_free 2023-01-04 12:31:22 +02:00
memcontrol.c mm: memcg: fix swapcached stat accounting 2022-12-11 18:12:20 -08:00
memfd.c
memory_hotplug.c mm: add pageblock_aligned() macro 2022-10-03 14:03:04 -07:00
memory-failure.c mm/memory-failure.c: cleanup in unpoison_memory 2022-11-30 15:59:08 -08:00
memory-tiers.c mm/demotion: fix NULL vs IS_ERR checking in memory_tier_init 2022-11-30 15:58:54 -08:00
memory.c mm: remove VM_FAULT_WRITE 2022-12-11 18:12:08 -08:00
mempolicy.c mm/mempolicy: fix memory leak in set_mempolicy_home_node system call 2022-12-21 14:31:51 -08:00
mempool.c mempool: do not use ksize() for poisoning 2022-11-30 15:58:41 -08:00
memremap.c mm/memremap.c: map FS_DAX device memory as decrypted 2022-11-08 15:57:23 -08:00
memtest.c
migrate_device.c mm/migrate_device: return number of migrating pages in args->cpages 2022-11-22 18:50:43 -08:00
migrate.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
mincore.c mm: convert find_get_incore_page() to filemap_get_incore_folio() 2022-11-08 17:37:18 -08:00
mlock.c mm/mlock: drop dead code in count_mm_mlocked_page_nr() 2022-09-26 19:46:27 -07:00
mm_init.c memory: move hotplug memory notifier priority to same file for easy sorting 2022-11-08 17:37:17 -08:00
mm_slot.h mm: introduce common struct mm_slot 2022-10-03 14:02:43 -07:00
mmap_lock.c
mmap.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
mmu_gather.c mm: mmu_gather: allow more than one batch of delayed rmaps 2022-12-11 18:12:21 -08:00
mmu_notifier.c
mmzone.c mm: multi-gen LRU: groundwork 2022-09-26 19:46:09 -07:00
mprotect.c New Feature: 2022-12-17 14:06:53 -06:00
mremap.c mm, mremap: fix mremap() expanding vma with addr inside vma 2022-12-21 14:31:51 -08:00
msync.c mm/msync: use vma_find() instead of vma linked list 2022-09-26 19:46:25 -07:00
nommu.c mm: remove the vma linked list 2022-09-26 19:46:26 -07:00
oom_kill.c mm: reduce noise in show_mem for lowmem allocations 2022-09-26 19:46:29 -07:00
page_alloc.c mm/page_alloc: update comments in __free_pages_ok() 2022-12-11 18:12:17 -08:00
page_counter.c mm: page_counter: remove unneeded atomic ops for low/min 2022-09-11 20:26:01 -07:00
page_ext.c Merge branch 'mm-hotfixes-stable' into mm-stable 2022-11-30 14:58:42 -08:00
page_idle.c mm: don't be stuck to rmap lock on reclaim path 2022-05-19 14:08:54 -07:00
page_io.c use less confusing names for iov_iter direction initializers 2022-11-25 13:01:55 -05:00
page_isolation.c mm/page_isolation: fix clang deadcode warning 2022-10-28 13:37:22 -07:00
page_owner.c mm: reuse pageblock_start/end_pfn() macro 2022-10-03 14:03:03 -07:00
page_poison.c
page_reporting.c mm/page_reporting: Add checks for page_reporting_order param 2022-11-28 16:48:19 +00:00
page_reporting.h
page_table_check.c mm: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
page_vma_mapped.c mm/swap: add swp_offset_pfn() to fetch PFN from swap entry 2022-09-26 19:46:05 -07:00
page-writeback.c mm: add bdi_set_min_ratio_no_scale() function 2022-11-30 15:59:06 -08:00
pagewalk.c mm/pagewalk: add walk_page_range_vma() 2022-12-11 18:12:08 -08:00
percpu-internal.h percpu: improve percpu_alloc_percpu event trace 2022-05-13 07:20:18 -07:00
percpu-km.c
percpu-stats.c
percpu-vm.c
percpu.c mm/percpu.c: remove the lcm code since block size is fixed at page size 2022-11-07 22:59:18 -08:00
pgalloc-track.h
pgtable-generic.c mm: avoid unnecessary flush on change_huge_pmd() 2022-05-13 07:20:05 -07:00
process_vm_access.c use less confusing names for iov_iter direction initializers 2022-11-25 13:01:55 -05:00
ptdump.c mm: pagewalk: Fix race between unmap and page walker 2022-09-03 10:13:13 -07:00
readahead.c mm: add PSI accounting around ->read_folio and ->readahead calls 2022-09-20 08:24:38 -06:00
rmap.c mm,thp,rmap: fix races between updates of subpages_mapcount 2022-12-11 18:12:20 -08:00
rodata_test.c mm/rodata_test: use PAGE_ALIGNED() helper 2022-10-03 14:03:05 -07:00
secretmem.c mm/secretmem: remove reduntant return value 2022-10-03 14:03:36 -07:00
shmem.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
shrinker_debug.c mm: shrinkers: fix double kfree on shrinker name 2022-07-29 18:07:13 -07:00
shuffle.c mm/shuffle: convert module_param_call to module_param_cb 2022-10-03 14:03:07 -07:00
shuffle.h
slab_common.c hardening updates for v6.2-rc1 2022-12-14 12:20:00 -08:00
slab.c Merge branch 'slab/for-6.2/kmalloc_redzone' into slab/for-next 2022-11-21 10:36:09 +01:00
slab.h Merge branch 'slub-tiny-v1r6' into slab/for-next 2022-12-01 00:14:00 +01:00
slob.c Merge branch 'slab/for-6.1/kmalloc_size_roundup' into slab/for-next 2022-09-29 11:30:55 +02:00
slub.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
sparse-vmemmap.c mm/sparse-vmemmap: generalise vmemmap_populate_hugepages() 2022-12-11 18:12:12 -08:00
sparse.c mm/hwpoison: introduce per-memory_block hwpoison counter 2022-11-08 17:37:22 -08:00
swap_cgroup.c mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled 2022-10-03 14:03:36 -07:00
swap_slots.c mm/swap: convert put_swap_page() to put_swap_folio() 2022-10-03 14:02:46 -07:00
swap_state.c mm: mmu_gather: prepare to gather encoded page pointers with flags 2022-11-30 15:58:50 -08:00
swap.c mm: teach release_pages() to take an array of encoded page pointers too 2022-11-30 15:58:50 -08:00
swap.h mm: convert find_get_incore_page() to filemap_get_incore_folio() 2022-11-08 17:37:18 -08:00
swapfile.c MM patches for 6.2-rc1. 2022-12-13 19:29:45 -08:00
truncate.c folio-compat: remove lru_cache_add() 2022-12-11 18:12:13 -08:00
usercopy.c mm: use kstrtobool() instead of strtobool() 2022-11-30 15:58:45 -08:00
userfaultfd.c New Feature: 2022-12-17 14:06:53 -06:00
util.c mm,thp,rmap: simplify compound page mapcount handling 2022-11-30 15:58:46 -08:00
vmalloc.c mm: vmalloc: use trace_free_vmap_area_noflush event 2022-11-08 17:37:17 -08:00
vmpressure.c
vmscan.c New Feature: 2022-12-17 14:06:53 -06:00
vmstat.c mm: vmscan: split khugepaged stats from direct reclaim stats 2022-11-30 15:58:41 -08:00
workingset.c folio-compat: remove lru_cache_add() 2022-12-11 18:12:13 -08:00
z3fold.c zpool: clean out dead code 2022-12-11 18:12:10 -08:00
zbud.c zpool: clean out dead code 2022-12-11 18:12:10 -08:00
zpool.c zpool: clean out dead code 2022-12-11 18:12:10 -08:00
zsmalloc.c zsmalloc: implement writeback mechanism for zsmalloc 2022-12-11 18:12:10 -08:00
zswap.c zswap: fix writeback lock ordering for zsmalloc 2022-12-11 18:12:09 -08:00