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Linus Torvalds 574823bfab Change mincore() to count "mapped" pages rather than "cached" pages 
The semantics of what "in core" means for the mincore() system call are
somewhat unclear, but Linux has always (since 2.3.52, which is when
mincore() was initially done) treated it as "page is available in page
cache" rather than "page is mapped in the mapping".

The problem with that traditional semantic is that it exposes a lot of
system cache state that it really probably shouldn't, and that users
shouldn't really even care about.

So let's try to avoid that information leak by simply changing the
semantics to be that mincore() counts actual mapped pages, not pages
that might be cheaply mapped if they were faulted (note the "might be"
part of the old semantics: being in the cache doesn't actually guarantee
that you can access them without IO anyway, since things like network
filesystems may have to revalidate the cache before use).

In many ways the old semantics were somewhat insane even aside from the
information leak issue.  From the very beginning (and that beginning is
a long time ago: 2.3.52 was released in March 2000, I think), the code
had a comment saying

  Later we can get more picky about what "in core" means precisely.

and this is that "later".  Admittedly it is much later than is really
comfortable.

NOTE! This is a real semantic change, and it is for example known to
change the output of "fincore", since that program literally does a
mmmap without populating it, and then doing "mincore()" on that mapping
that doesn't actually have any pages in it.

I'm hoping that nobody actually has any workflow that cares, and the
info leak is real.

We may have to do something different if it turns out that people have
valid reasons to want the old semantics, and if we can limit the
information leak sanely.

Cc: Kevin Easton <kevin@guarana.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Masatake YAMATO <yamato@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2019-01-06 13:43:02 -08:00
..
kasan mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
Kconfig ksm: replace jhash2 with xxhash 2018-12-28 12:11:46 -08:00
Kconfig.debug mm: clarify CONFIG_PAGE_POISONING and usage 2018-08-22 10:52:44 -07:00
Makefile mm: remove nobootmem 2018-10-31 08:54:16 -07:00
backing-dev.c blkcg: delay blkg destruction until after writeback has finished 2018-08-31 14:48:56 -06:00
balloon_compaction.c virtio_balloon: fix deadlock on OOM 2017-11-14 23:57:38 +02:00
cleancache.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
cma.c kasan, mm, arm64: tag non slab memory allocated via pagealloc 2018-12-28 12:11:44 -08:00
cma.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
cma_debug.c mm/cma: remove unsupported gfp_mask parameter from cma_alloc() 2018-08-17 16:20:32 -07:00
compaction.c mm: move zone watermark accesses behind an accessor 2018-12-28 12:11:48 -08:00
debug.c mm/debug.c: make "migrate_reason_names[]" const char * 2018-12-28 12:11:48 -08:00
debug_page_ref.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dmapool.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
early_ioremap.c mm/early_ioremap: Fix boot hang with earlyprintk=efi,keep 2017-12-11 14:54:44 +01:00
fadvise.c vfs: implement readahead(2) using POSIX_FADV_WILLNEED 2018-08-30 20:01:32 +02:00
failslab.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
filemap.c mm/: remove caller signal_pending branch predictions 2019-01-04 13:13:48 -08:00
frame_vector.c mm/frame_vector.c: release a semaphore in 'get_vaddr_frames()' 2017-12-14 16:00:48 -08:00
frontswap.c mm: use octal not symbolic permissions 2018-06-15 07:55:25 +09:00
gup.c Merge branch 'akpm' (patches from Andrew) 2019-01-05 09:16:18 -08:00
gup_benchmark.c mm/gup_benchmark.c: prevent integer overflow in ioctl 2018-10-31 08:54:12 -07:00
highmem.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
hmm.c mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm 2018-12-28 12:11:52 -08:00
huge_memory.c mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
hugetlb.c mm/: remove caller signal_pending branch predictions 2019-01-04 13:13:48 -08:00
hugetlb_cgroup.c mm: rename page_counter's count/limit into usage/max 2018-06-07 17:34:35 -07:00
hwpoison-inject.c mm/memory_failure: Remove unused trapno from memory_failure 2018-01-23 12:17:42 -06:00
init-mm.c mm: Allocate the mm_cpumask (mm->cpu_bitmap[]) dynamically based on nr_cpu_ids 2018-07-17 09:35:30 +02:00
internal.h mm: use alloc_flags to record if kswapd can wake 2018-12-28 12:11:48 -08:00
interval_tree.c mm/interval_tree.c: use vma_pages() helper 2018-01-31 17:18:37 -08:00
khugepaged.c mm/mmu_notifier: use structure for invalidate_range_start/end calls v2 2018-12-28 12:11:50 -08:00
kmemleak-test.c
…
kmemleak.c kmemleak: add config to select auto scan 2018-12-28 12:11:51 -08:00
ksm.c ksm: react on changing "sleep_millisecs" parameter faster 2018-12-28 12:11:51 -08:00
list_lru.c mm/list_lru: introduce list_lru_shrink_walk_irq() 2018-08-17 16:20:32 -07:00
maccess.c x86/fault: BUG() when uaccess helpers fault on kernel addresses 2018-09-03 15:12:09 +02:00
madvise.c mm/mmu_notifier: use structure for invalidate_range_start/end calls v2 2018-12-28 12:11:50 -08:00
memblock.c mm/memblock.c: skip kmemleak for kasan_init() 2018-12-28 12:11:49 -08:00
memcontrol.c memcg, oom: notify on oom killer invocation from the charge path 2018-12-28 12:11:52 -08:00
memfd.c memfd: Convert memfd_tag_pins to XArray 2018-10-21 10:46:41 -04:00
memory-failure.c hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization 2018-12-28 12:11:51 -08:00
memory.c mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
memory_hotplug.c mm, memory_hotplug: deobfuscate migration part of offlining 2018-12-28 12:11:50 -08:00
mempolicy.c Revert "mm, thp: consolidate THP gfp handling into alloc_hugepage_direct_gfpmask" 2018-12-08 10:26:20 -08:00
mempool.c mm/mempool.c: add missing parameter description 2018-08-22 10:52:44 -07:00
memtest.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
migrate.c mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
mincore.c Change mincore() to count "mapped" pages rather than "cached" pages 2019-01-06 13:43:02 -08:00
mlock.c dax: remove VM_MIXEDMAP for fsdax and device dax 2018-08-17 16:20:27 -07:00
mm_init.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
mmap.c mm/mmap.c: remove verify_mm_writelocked() 2018-12-28 12:11:47 -08:00
mmu_context.c
…
mmu_gather.c mm: Replace call_rcu_sched() with call_rcu() 2018-11-27 09:21:46 -08:00
mmu_notifier.c mm/mmu_notifier: use structure for invalidate_range_start/end calls v2 2018-12-28 12:11:50 -08:00
mmzone.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
mprotect.c mm/mmu_notifier: use structure for invalidate_range_start/end calls v2 2018-12-28 12:11:50 -08:00
mremap.c mm: speed up mremap by 20x on large regions 2019-01-04 13:13:48 -08:00
msync.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
nommu.c mm/gup: cache dev_pagemap while pinning pages 2018-10-26 16:38:15 -07:00
oom_kill.c mm/mmu_notifier: use structure for invalidate_range_start/end calls v2 2018-12-28 12:11:50 -08:00
page-writeback.c mm/page-writeback.c: don't break integrity writeback on ->writepage() error 2018-12-28 12:11:49 -08:00
page_alloc.c mm/page_alloc.c: allow error injection 2018-12-28 12:11:51 -08:00
page_counter.c memcg: introduce memory.min 2018-06-07 17:34:36 -07:00
page_ext.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
page_idle.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
page_io.c mm/page_io.c: fix polled swap page in 2019-01-04 13:13:48 -08:00
page_isolation.c mm: only report isolation failures when offlining memory 2018-12-28 12:11:46 -08:00
page_owner.c mm/page_owner: clamp read count to PAGE_SIZE 2018-12-28 12:11:46 -08:00
page_poison.c virtio, vhost: fixes, tweaks 2018-11-01 14:42:49 -07:00
page_vma_mapped.c mm/rmap: map_pte() was not handling private ZONE_DEVICE page properly 2018-10-31 08:54:11 -07:00
pagewalk.c mm: kernel-doc: add missing parameter descriptions 2018-04-05 21:36:27 -07:00
percpu-internal.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
percpu-km.c percpu: convert spin_lock_irq to spin_lock_irqsave. 2018-12-18 09:04:08 -08:00
percpu-stats.c treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
percpu-vm.c percpu: allow select gfp to be passed to underlying allocators 2018-02-18 05:33:01 -08:00
percpu.c Merge branch 'for-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/dennis/percpu 2018-11-01 09:27:57 -07:00
pgtable-generic.c x86/mm: Page size aware flush_tlb_mm_range() 2018-10-09 16:51:11 +02:00
process_vm_access.c mm: docs: add blank lines to silence sphinx "Unexpected indentation" errors 2018-02-06 18:32:48 -08:00
quicklist.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
readahead.c mm/readahead.c: simplify get_next_ra_size() 2018-12-28 12:11:46 -08:00
rmap.c hugetlbfs: use i_mmap_rwsem for more pmd sharing synchronization 2018-12-28 12:11:51 -08:00
rodata_test.c
…
shmem.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
slab.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
slab.h kasan, mm: change hooks signatures 2018-12-28 12:11:43 -08:00
slab_common.c A fairly normal cycle for documentation stuff. We have a new 2018-12-29 11:21:49 -08:00
slob.c slab: __GFP_ZERO is incompatible with a constructor 2018-06-07 17:34:34 -07:00
slub.c mm/slub.c: record final state of slub action in deactivate_slab() 2018-12-28 12:11:46 -08:00
sparse-vmemmap.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
sparse.c mm, sparse: pass nid instead of pgdat to sparse_add_one_section() 2018-12-28 12:11:49 -08:00
swap.c fs: don't open code lru_to_page() 2019-01-04 13:13:48 -08:00
swap_cgroup.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
swap_slots.c mm, swap, get_swap_pages: use entry_size instead of cluster in parameter 2018-08-22 10:52:44 -07:00
swap_state.c Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-dax 2018-10-28 11:35:40 -07:00
swapfile.c mm, swap: fix swapoff with KSM pages 2018-12-28 12:11:52 -08:00
truncate.c mm: cleancache: fix corruption on missed inode invalidation 2018-11-30 14:56:14 -08:00
usercopy.c usercopy: Allow boot cmdline disabling of hardening 2018-07-04 08:04:52 -07:00
userfaultfd.c mm: treewide: remove unused address argument from pte_alloc functions 2019-01-04 13:13:47 -08:00
util.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
vmacache.c mm: get rid of vmacache_flush_all() entirely 2018-09-13 15:18:04 -10:00
vmalloc.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
vmpressure.c mm/vmpressure.c: convert to use match_string() helper 2018-06-07 17:34:36 -07:00
vmscan.c mm: put_and_wait_on_page_locked() while page is migrated 2018-12-28 12:11:48 -08:00
vmstat.c mm: convert zone->managed_pages to atomic variable 2018-12-28 12:11:47 -08:00
workingset.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
z3fold.c z3fold: fix possible reclaim races 2018-11-18 10:15:09 -08:00
zbud.c mm: docs: fix parameter names mismatch 2018-02-06 18:32:48 -08:00
zpool.c mm/zpool.c: zpool_evictable: fix mismatch in parameter name and kernel-doc 2018-02-21 15:35:43 -08:00
zsmalloc.c mm/zsmalloc.c: fix fall-through annotation 2018-10-26 16:26:35 -07:00
zswap.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00