linux/mm
Vinayak Menon 5df373e956 mm/page_io.c: do not free shared swap slots
The following race is observed due to which a processes faulting on a
swap entry, finds the page neither in swapcache nor swap.  This causes
zram to give a zero filled page that gets mapped to the process,
resulting in a user space crash later.

Consider parent and child processes Pa and Pb sharing the same swap slot
with swap_count 2.  Swap is on zram with SWP_SYNCHRONOUS_IO set.
Virtual address 'VA' of Pa and Pb points to the shared swap entry.

Pa                                       Pb

fault on VA                              fault on VA
do_swap_page                             do_swap_page
lookup_swap_cache fails                  lookup_swap_cache fails
                                         Pb scheduled out
swapin_readahead (deletes zram entry)
swap_free (makes swap_count 1)
                                         Pb scheduled in
                                         swap_readpage (swap_count == 1)
                                         Takes SWP_SYNCHRONOUS_IO path
                                         zram enrty absent
                                         zram gives a zero filled page

Fix this by making sure that swap slot is freed only when swap count
drops down to one.

Link: http://lkml.kernel.org/r/1571743294-14285-1-git-send-email-vinmenon@codeaurora.org
Fixes: aa8d22a11d ("mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference")
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Suggested-by: Minchan Kim <minchan@google.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-11-15 18:34:00 -08:00
..
kasan mm: introduce compound_nr() 2019-09-24 15:54:08 -07:00
backing-dev.c bdi: Do not use freezable workqueue 2019-10-06 09:11:35 -06:00
balloon_compaction.c mm/balloon_compaction: suppress allocation warnings 2019-09-04 07:42:01 -04:00
cleancache.c Driver Core and debugfs changes for 5.3-rc1 2019-07-12 12:24:03 -07:00
cma_debug.c mm/cma_debug.c: fix the break condition in cma_maxchunk_get() 2019-05-14 09:47:45 -07:00
cma.c mm/cma.c: fail if fixed declaration can't be honored 2019-07-16 19:23:21 -07:00
cma.h
compaction.c mm, compaction: fix wrong pfn handling in __reset_isolation_pfn() 2019-10-14 15:04:01 -07:00
debug_page_ref.c
debug.c mm: update references to page _refcount 2019-05-14 19:52:47 -07:00
dmapool.c mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options 2019-07-12 11:05:46 -07:00
early_ioremap.c
fadvise.c fs: Export generic_fadvise() 2019-08-30 22:43:58 -07:00
failslab.c mm/failslab.c: by default, do not fail allocations with direct reclaim only 2019-07-12 11:05:43 -07:00
filemap.c mm/filemap.c: include <linux/ramfs.h> for generic_file_vm_ops definition 2019-10-19 06:32:32 -04:00
frame_vector.c mm: untag user pointers in get_vaddr_frames 2019-09-25 17:51:41 -07:00
frontswap.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 482 2019-06-19 17:09:52 +02:00
gup_benchmark.c mm/gup: replace get_user_pages_longterm() with FOLL_LONGTERM 2019-05-14 09:47:45 -07:00
gup.c mm/gup: fix a misnamed "write" argument, and a related bug 2019-10-19 06:32:32 -04:00
highmem.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
hmm.c pagewalk: separate function pointers from iterator data 2019-09-07 04:28:04 -03:00
huge_memory.c mm/thp: fix node page state in split_huge_page_to_list() 2019-10-19 06:32:32 -04:00
hugetlb_cgroup.c mm: hugetlb: switch to css_tryget() in hugetlb_cgroup_charge_cgroup() 2019-11-15 18:34:00 -08:00
hugetlb.c hugetlbfs: don't access uninitialized memmaps in pfn_range_valid_gigantic() 2019-10-19 06:32:32 -04:00
hwpoison-inject.c hwpoison-inject: no need to check return value of debugfs_create functions 2019-06-03 15:39:40 +02:00
init-mm.c mm/init-mm.c: include <linux/mman.h> for vm_committed_as_batch 2019-10-19 06:32:32 -04:00
internal.h mm: introduce MADV_COLD 2019-09-25 17:51:41 -07:00
interval_tree.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 248 2019-06-19 17:09:08 +02:00
Kconfig mm,thp: add read-only THP support for (non-shmem) FS 2019-09-24 15:54:11 -07:00
Kconfig.debug mm, page_owner, debug_pagealloc: save and dump freeing stack trace 2019-09-24 15:54:08 -07:00
khugepaged.c mm,thp: recheck each page before collapsing file THP 2019-11-15 18:34:00 -08:00
kmemleak-test.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 333 2019-06-05 17:37:06 +02:00
kmemleak.c kmemleak: Do not corrupt the object_list during clean-up 2019-10-14 08:56:16 -07:00
ksm.c mm: move memcmp_pages() and pages_identical() 2019-09-24 15:54:11 -07:00
list_lru.c mm: memcg/slab: stop setting page->mem_cgroup pointer for slab pages 2019-07-12 11:05:44 -07:00
maccess.c The main changes in this release include: 2019-07-18 11:51:00 -07:00
madvise.c mm: fix trying to reclaim unevictable lru page when calling madvise_pageout 2019-11-15 18:33:59 -08:00
Makefile mm: silence -Woverride-init/initializer-overrides 2019-09-24 15:54:10 -07:00
memblock.c mm: memblock: do not enforce current limit for memblock_phys* family 2019-10-19 06:32:32 -04:00
memcontrol.c mm: memcg: switch to css_tryget() in get_mem_cgroup_from_mm() 2019-11-15 18:34:00 -08:00
memfd.c mm: page cache: store only head pages in i_pages 2019-09-24 15:54:08 -07:00
memory_hotplug.c mm/memory_hotplug: fix try_offline_node() 2019-11-15 18:34:00 -08:00
memory-failure.c mm/memory-failure.c: don't access uninitialized memmaps in memory_failure() 2019-10-19 06:32:31 -04:00
memory.c mm: do not hash address in print_bad_pte() 2019-09-24 15:54:09 -07:00
mempolicy.c mm: mempolicy: fix the wrong return value and potential pages leak of mbind 2019-11-15 18:33:59 -08:00
mempool.c docs/core-api/mm: fix return value descriptions in mm/ 2019-03-05 21:07:20 -08:00
memremap.c mm/memunmap: don't access uninitialized memmap in memunmap_pages() 2019-10-19 06:32:32 -04:00
memtest.c
migrate.c mm: untag user pointers passed to memory syscalls 2019-09-25 17:51:41 -07:00
mincore.c mm: untag user pointers passed to memory syscalls 2019-09-25 17:51:41 -07:00
mlock.c mm: untag user pointers passed to memory syscalls 2019-09-25 17:51:41 -07:00
mm_init.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
mmap.c mm: untag user pointers in mmap/munmap/mremap/brk 2019-09-25 17:51:41 -07:00
mmu_context.c
mmu_gather.c mm: remove quicklist page table caches 2019-09-24 15:54:09 -07:00
mmu_notifier.c mm/mmu_notifiers: use the right return code for WARN_ON 2019-11-06 08:47:50 -08:00
mmzone.c
mprotect.c mm: untag user pointers passed to memory syscalls 2019-09-25 17:51:41 -07:00
mremap.c mm: untag user pointers in mmap/munmap/mremap/brk 2019-09-25 17:51:41 -07:00
msync.c mm: untag user pointers passed to memory syscalls 2019-09-25 17:51:41 -07:00
nommu.c mm: introduce page_size() 2019-09-24 15:54:08 -07:00
oom_kill.c mm: introduce MADV_COLD 2019-09-25 17:51:41 -07:00
page_alloc.c mm/page_alloc.c: ratelimit allocation failure warnings more aggressively 2019-11-06 08:47:50 -08:00
page_counter.c
page_ext.c mm, page_owner: fix off-by-one error in __set_page_owner_handle() 2019-10-14 15:04:00 -07:00
page_idle.c mm/page_idle.c: fix oops because end_pfn is larger than max_pfn 2019-06-29 16:43:45 +08:00
page_io.c mm/page_io.c: do not free shared swap slots 2019-11-15 18:34:00 -08:00
page_isolation.c mm/page_isolation.c: change the prototype of undo_isolate_page_range() 2019-07-12 11:05:43 -07:00
page_owner.c mm/page_owner: don't access uninitialized memmaps when reading /proc/pagetypeinfo 2019-10-19 06:32:31 -04:00
page_poison.c mm/page_poison.c: fix a typo in a comment 2019-09-24 15:54:08 -07:00
page_vma_mapped.c mm: introduce page_size() 2019-09-24 15:54:08 -07:00
page-writeback.c writeback, memcg: Implement foreign dirty flushing 2019-08-27 09:22:38 -06:00
pagewalk.c pagewalk: use lockdep_assert_held for locking validation 2019-09-07 04:28:04 -03:00
percpu-internal.h percpu: convert chunk hints to be based on pcpu_block_md 2019-03-13 12:25:31 -07:00
percpu-km.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
percpu-stats.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
percpu-vm.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 428 2019-06-05 17:37:16 +02:00
percpu.c percpu: Use struct_size() helper 2019-09-04 13:40:49 -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 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
readahead.c treewide: Add SPDX license identifier for missed files 2019-05-21 10:50:45 +02:00
rmap.c mm: include <linux/huge_mm.h> for is_vma_temporary_stack 2019-10-19 06:32:32 -04:00
rodata_test.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00
shmem.c Merge branch 'work.mount3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-10-10 08:16:44 -07:00
shuffle.c mm: fix -Wmissing-prototypes warnings 2019-10-07 15:47:19 -07:00
shuffle.h mm: maintain randomization of page free lists 2019-05-14 19:52:48 -07:00
slab_common.c mm: memcg/slab: fix panic in __free_slab() caused by premature memcg pointer release 2019-10-19 06:32:32 -04:00
slab.c mm/slab.c: fix kernel-doc warning for __ksize() 2019-10-14 15:04:01 -07:00
slab.h mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly 2019-11-06 08:47:50 -08:00
slob.c mm, sl[aou]b: guarantee natural alignment for kmalloc(power-of-two) 2019-10-07 15:47:20 -07:00
slub.c mm: slub: really fix slab walking for init_on_free 2019-11-15 18:34:00 -08:00
sparse-vmemmap.c mm/sparsemem: convert kmalloc_section_memmap() to populate_section_memmap() 2019-07-18 17:08:07 -07:00
sparse.c mm: fix -Wmissing-prototypes warnings 2019-10-07 15:47:19 -07:00
swap_cgroup.c
swap_slots.c
swap_state.c mm: page cache: store only head pages in i_pages 2019-09-24 15:54:08 -07:00
swap.c mm: introduce MADV_COLD 2019-09-25 17:51:41 -07:00
swapfile.c vfs: don't allow writes to swap files 2019-08-20 07:55:16 -07:00
truncate.c mm/thp: allow dropping THP from page cache 2019-10-19 06:32:33 -04:00
usercopy.c usercopy: Avoid HIGHMEM pfn warning 2019-09-17 15:20:17 -07:00
userfaultfd.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 499 2019-06-19 17:09:53 +02:00
util.c arm64, mm: make randomization selected by generic topdown mmap layout 2019-09-24 15:54:11 -07:00
vmacache.c mm: get rid of vmacache_flush_all() entirely 2018-09-13 15:18:04 -10:00
vmalloc.c augmented rbtree: add new RB_DECLARE_CALLBACKS_MAX macro 2019-09-25 17:51:39 -07:00
vmpressure.c mm/vmpressure.c: fix a signedness bug in vmpressure_register_event() 2019-10-07 15:47:19 -07:00
vmscan.c mm/vmscan.c: support removing arbitrary sized pages from mapping 2019-10-19 06:32:32 -04:00
vmstat.c mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo 2019-11-06 08:47:50 -08:00
workingset.c mm: workingset: fix vmstat counters for shadow nodes 2019-08-13 16:06:52 -07:00
z3fold.c mm/z3fold.c: claim page in the beginning of free 2019-10-07 15:47:19 -07:00
zbud.c treewide: Add SPDX license identifier for more missed files 2019-05-21 10:50:45 +02:00
zpool.c zpool: add malloc_support_movable to zpool_driver 2019-09-24 15:54:12 -07:00
zsmalloc.c mm/zsmalloc.c: fix a -Wunused-function warning 2019-09-24 15:54:12 -07:00
zswap.c zswap: do not map same object twice 2019-09-24 15:54:12 -07:00