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Shakeel Butt cefc7ef3c8 mm, oom: fix use-after-free in oom_kill_process 
Syzbot instance running on upstream kernel found a use-after-free bug in
oom_kill_process.  On further inspection it seems like the process
selected to be oom-killed has exited even before reaching
read_lock(&tasklist_lock) in oom_kill_process().  More specifically the
tsk->usage is 1 which is due to get_task_struct() in oom_evaluate_task()
and the put_task_struct within for_each_thread() frees the tsk and
for_each_thread() tries to access the tsk.  The easiest fix is to do
get/put across the for_each_thread() on the selected task.

Now the next question is should we continue with the oom-kill as the
previously selected task has exited? However before adding more
complexity and heuristics, let's answer why we even look at the children
of oom-kill selected task? The select_bad_process() has already selected
the worst process in the system/memcg.  Due to race, the selected
process might not be the worst at the kill time but does that matter?
The userspace can use the oom_score_adj interface to prefer children to
be killed before the parent.  I looked at the history but it seems like
this is there before git history.

Link: http://lkml.kernel.org/r/20190121215850.221745-1-shakeelb@google.com
Reported-by: syzbot+7fbbfa368521945f0e3d@syzkaller.appspotmail.com
Fixes: 6b0c81b3be ("mm, oom: reduce dependency on tasklist_lock")
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Roman Gushchin <guro@fb.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2019-02-01 15:46:23 -08:00
..
kasan kasan: fix krealloc handling for tag-based mode 2019-01-08 17:15:11 -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 writeback: synchronize sync(2) against cgroup writeback membership switches 2019-01-22 14:39:38 -07:00
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/hugetlb.c: teach follow_hugetlb_page() to handle FOLL_NOWAIT 2019-02-01 15:46:23 -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: revert "use i_mmap_rwsem for more pmd sharing synchronization" 2019-01-08 17:15:11 -08:00
memory.c mm/memory.c: initialise mmu_notifier_range correctly 2019-01-08 17:15:11 -08:00
memory_hotplug.c mm,memory_hotplug: fix scan_movable_pages() for gigantic hugepages 2019-02-01 15:46:23 -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: migrate: make buffer_migrate_page_norefs() actually succeed 2019-02-01 15:46:23 -08:00
mincore.c Revert "Change mincore() to count "mapped" pages rather than "cached" pages" 2019-01-24 09:04:37 +13:00
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, oom: fix use-after-free in oom_kill_process 2019-02-01 15:46:23 -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 Revert "mm, memory_hotplug: initialize struct pages for the full memory section" 2019-01-28 10:35:22 -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 mm/mmu_notifier: mm/rmap.c: Fix a mmu_notifier range bug in try_to_unmap_one 2019-01-10 02:58:21 -08:00
rodata_test.c mm: fix RODATA_TEST failure "rodata_test: test data was not read only" 2017-10-03 17:54:24 -07:00
shmem.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
slab.c slab: alien caches must not be initialized if the allocation of the alien cache failed 2019-01-08 17:15:11 -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 kasan: make tag based mode work with CONFIG_HARDENED_USERCOPY 2019-01-08 17:15:11 -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 mm/usercopy.c: no check page span for stack objects 2019-01-08 17:15:11 -08:00
userfaultfd.c hugetlbfs: revert "use i_mmap_rwsem for more pmd sharing synchronization" 2019-01-08 17:15:11 -08:00
util.c mm: page_mapped: don't assume compound page is huge or THP 2019-01-08 17:15:11 -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