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64e455079e
linux/mm
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Peter Feiner 64e455079e mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared 
For VMAs that don't want write notifications, PTEs created for read faults
have their write bit set.  If the read fault happens after VM_SOFTDIRTY is
cleared, then the PTE's softdirty bit will remain clear after subsequent
writes.

Here's a simple code snippet to demonstrate the bug:

  char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE,
                 MAP_ANONYMOUS | MAP_SHARED, -1, 0);
  system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */
  assert(*m == '\0');     /* new PTE allows write access */
  assert(!soft_dirty(x));
  *m = 'x';               /* should dirty the page */
  assert(soft_dirty(x));  /* fails */

With this patch, write notifications are enabled when VM_SOFTDIRTY is
cleared.  Furthermore, to avoid unnecessary faults, write notifications
are disabled when VM_SOFTDIRTY is set.

As a side effect of enabling and disabling write notifications with
care, this patch fixes a bug in mprotect where vm_page_prot bits set by
drivers were zapped on mprotect.  An analogous bug was fixed in mmap by
commit c9d0bf2414 ("mm: uncached vma support with writenotify").

Signed-off-by: Peter Feiner <pfeiner@google.com>
Reported-by: Peter Feiner <pfeiner@google.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-10-14 02:18:28 +02:00
..
backing-dev.c Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-10 07:26:02 -04:00
balloon_compaction.c mm/balloon_compaction: add vmstat counters and kpageflags bit 2014-10-09 22:26:01 -04:00
bootmem.c mm/bootmem.c: use include/linux/ headers 2014-10-09 22:26:00 -04:00
cleancache.c
cma.c drivers: dma-contiguous: add initialization from device tree 2014-10-14 02:18:12 +02:00
compaction.c mm/balloon_compaction: redesign ballooned pages management 2014-10-09 22:26:01 -04:00
debug-pagealloc.c
debug.c mm/debug.c: use pr_emerg() 2014-10-09 22:25:59 -04:00
dmapool.c mm/dmapool.c: fixed a brace coding style issue 2014-10-09 22:26:00 -04:00
early_ioremap.c
fadvise.c
failslab.c
filemap_xip.c
filemap.c mm/filemap.c: remove trailing whitespace 2014-10-09 22:26:00 -04:00
fremap.c
frontswap.c
gup.c mm: introduce a general RCU get_user_pages_fast() 2014-10-09 22:26:00 -04:00
highmem.c mm/highmem: make kmap cache coloring aware 2014-08-06 18:01:22 -07:00
huge_memory.c mm: use VM_BUG_ON_MM where possible 2014-10-09 22:25:58 -04:00
hugetlb_cgroup.c hugetlb_cgroup: use lockdep_assert_held rather than spin_is_locked 2014-08-29 16:28:16 -07:00
hugetlb.c mm: convert a few VM_BUG_ON callers to VM_BUG_ON_VMA 2014-10-09 22:25:57 -04:00
hwpoison-inject.c mm/hwpoison-inject.c: remove unnecessary null test before debugfs_remove_recursive 2014-08-06 18:01:19 -07:00
init-mm.c
internal.h mm, compaction: pass gfp mask to compact_control 2014-10-09 22:25:55 -04:00
interval_tree.c mm: convert a few VM_BUG_ON callers to VM_BUG_ON_VMA 2014-10-09 22:25:57 -04:00
iov_iter.c Add copy_to_iter(), copy_from_iter() and iov_iter_zero() 2014-10-09 02:39:03 -04:00
Kconfig mm/balloon_compaction: add vmstat counters and kpageflags bit 2014-10-09 22:26:01 -04:00
Kconfig.debug
kmemcheck.c mm/slab_common: move kmem_cache definition to internal header 2014-10-09 22:25:50 -04:00
kmemleak-test.c
kmemleak.c
ksm.c mm: ksm use pr_err instead of printk 2014-10-09 22:26:00 -04:00
list_lru.c
maccess.c
madvise.c mm: update the description for madvise_remove 2014-08-06 18:01:18 -07:00
Makefile Fixup for 3.18: use PATCHv2 of "mm: Support compiling out madvise and fadvise" 2014-10-12 09:21:57 -04:00
memblock.c mem-hotplug: let memblock skip the hotpluggable memory regions in __next_mem_range() 2014-09-10 15:42:12 -07:00
memcontrol.c memcg: zap memcg_can_account_kmem 2014-10-09 22:26:00 -04:00
memory_hotplug.c memory-hotplug: add sysfs valid_zones attribute 2014-10-09 22:25:52 -04:00
memory-failure.c cgroup: remove redundant check in cgroup_ino() 2014-09-19 09:16:23 -04:00
memory.c mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared 2014-10-14 02:18:28 +02:00
mempolicy.c mm: mempolicy: skip inaccessible VMAs when setting MPOL_MF_LAZY 2014-10-09 22:26:02 -04:00
mempool.c
migrate.c mm/balloon_compaction: redesign ballooned pages management 2014-10-09 22:26:01 -04:00
mincore.c
mlock.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2014-10-13 15:44:12 +02:00
mm_init.c
mmap.c mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared 2014-10-14 02:18:28 +02:00
mmu_context.c
mmu_notifier.c kvm: Fix page ageing bugs 2014-09-24 14:07:58 +02:00
mmzone.c
mprotect.c mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared 2014-10-14 02:18:28 +02:00
mremap.c mm/mremap.c: use linux headers 2014-10-09 22:26:00 -04:00
msync.c msync: fix incorrect fstart calculation 2014-07-03 09:21:53 -07:00
nobootmem.c mem-hotplug: let memblock skip the hotpluggable memory regions in __next_mem_range() 2014-09-10 15:42:12 -07:00
nommu.c percpu_counter: add @gfp to percpu_counter_init() 2014-09-08 09:51:29 +09:00
oom_kill.c mm: clean up zone flags 2014-10-09 22:25:57 -04:00
page_alloc.c mm: move debug code out of page_alloc.c 2014-10-09 22:25:58 -04:00
page_cgroup.c
page_io.c
page_isolation.c
page-writeback.c Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-10 07:26:02 -04:00
pagewalk.c mm: use VM_BUG_ON_MM where possible 2014-10-09 22:25:58 -04:00
percpu-km.c percpu: implmeent pcpu_nr_empty_pop_pages and chunk->nr_populated 2014-09-02 14:46:05 -04:00
percpu-vm.c percpu: move region iterations out of pcpu_[de]populate_chunk() 2014-09-02 14:46:02 -04:00
percpu.c percpu: fix how @gfp is interpreted by the percpu allocator 2014-10-08 12:01:52 -04:00
pgtable-generic.c mm: actually clear pmd_numa before invalidating 2014-08-29 16:28:15 -07:00
process_vm_access.c
quicklist.c
readahead.c mm/readahead.c: remove unused file_ra_state from count_history_pages 2014-08-06 18:01:15 -07:00
rmap.c mm: convert a few VM_BUG_ON callers to VM_BUG_ON_VMA 2014-10-09 22:25:57 -04:00
shmem.c Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2014-10-10 07:26:02 -04:00
slab_common.c memcg: move memcg_update_cache_size() to slab_common.c 2014-10-09 22:25:59 -04:00
slab.c mm/slab: fix unaligned access on sparc64 2014-10-14 02:18:12 +02:00
slab.h mm/slab: use percpu allocator for cpu cache 2014-10-09 22:25:51 -04:00
slob.c mm/sl[ao]b: always track caller in kmalloc_(node_)track_caller() 2014-10-09 22:25:50 -04:00
slub.c mm/slab_common: commonize slab merge logic 2014-10-09 22:25:51 -04:00
sparse-vmemmap.c
sparse.c
swap_state.c mm: memcontrol: do not kill uncharge batching in free_pages_and_swap_cache 2014-10-09 22:25:59 -04:00
swap.c mm: memcontrol: do not kill uncharge batching in free_pages_and_swap_cache 2014-10-09 22:25:59 -04:00
swapfile.c mm: memcontrol: rewrite uncharge API 2014-08-08 15:57:17 -07:00
truncate.c mm: memcontrol: rewrite uncharge API 2014-08-08 15:57:17 -07:00
util.c proc/maps: make vm_is_stack() logic namespace-friendly 2014-10-09 22:25:50 -04:00
vmacache.c
vmalloc.c mm/vmalloc.c: use seq_open_private() instead of seq_open() 2014-10-09 22:25:56 -04:00
vmpressure.c
vmscan.c mm: memcontrol: fix transparent huge page allocations under pressure 2014-10-09 22:25:59 -04:00
vmstat.c vmstat: on-demand vmstat workers V8 2014-10-09 22:26:02 -04:00
workingset.c
zbud.c zbud: avoid accessing last unused freelist 2014-10-09 22:26:03 -04:00
zpool.c mm/zpool: use prefixed module loading 2014-08-29 16:28:16 -07:00
zsmalloc.c zsmalloc: simplify init_zspage free obj linking 2014-10-09 22:26:03 -04:00
zswap.c mm/zswap.c: add __init to zswap_entry_cache_destroy() 2014-08-08 15:57:18 -07:00