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Miles Chen c4de112347 mm/memcontrol.c: fix use after free in mem_cgroup_iter() 
commit 54a83d6bcbf8f4700013766b974bf9190d40b689 upstream.

This patch is sent to report an use after free in mem_cgroup_iter()
after merging commit be2657752e9e ("mm: memcg: fix use after free in
mem_cgroup_iter()").

I work with android kernel tree (4.9 & 4.14), and commit be2657752e9e
("mm: memcg: fix use after free in mem_cgroup_iter()") has been merged
to the trees.  However, I can still observe use after free issues
addressed in the commit be2657752e9e.  (on low-end devices, a few times
this month)

backtrace:
        css_tryget <- crash here
        mem_cgroup_iter
        shrink_node
        shrink_zones
        do_try_to_free_pages
        try_to_free_pages
        __perform_reclaim
        __alloc_pages_direct_reclaim
        __alloc_pages_slowpath
        __alloc_pages_nodemask

To debug, I poisoned mem_cgroup before freeing it:

  static void __mem_cgroup_free(struct mem_cgroup *memcg)
        for_each_node(node)
        free_mem_cgroup_per_node_info(memcg, node);
        free_percpu(memcg->stat);
  +     /* poison memcg before freeing it */
  +     memset(memcg, 0x78, sizeof(struct mem_cgroup));
        kfree(memcg);
  }

The coredump shows the position=0xdbbc2a00 is freed.

  (gdb) p/x ((struct mem_cgroup_per_node *)0xe5009e00)->iter[8]
  $13 = {position = 0xdbbc2a00, generation = 0x2efd}

  0xdbbc2a00:     0xdbbc2e00      0x00000000      0xdbbc2800      0x00000100
  0xdbbc2a10:     0x00000200      0x78787878      0x00026218      0x00000000
  0xdbbc2a20:     0xdcad6000      0x00000001      0x78787800      0x00000000
  0xdbbc2a30:     0x78780000      0x00000000      0x0068fb84      0x78787878
  0xdbbc2a40:     0x78787878      0x78787878      0x78787878      0xe3fa5cc0
  0xdbbc2a50:     0x78787878      0x78787878      0x00000000      0x00000000
  0xdbbc2a60:     0x00000000      0x00000000      0x00000000      0x00000000
  0xdbbc2a70:     0x00000000      0x00000000      0x00000000      0x00000000
  0xdbbc2a80:     0x00000000      0x00000000      0x00000000      0x00000000
  0xdbbc2a90:     0x00000001      0x00000000      0x00000000      0x00100000
  0xdbbc2aa0:     0x00000001      0xdbbc2ac8      0x00000000      0x00000000
  0xdbbc2ab0:     0x00000000      0x00000000      0x00000000      0x00000000
  0xdbbc2ac0:     0x00000000      0x00000000      0xe5b02618      0x00001000
  0xdbbc2ad0:     0x00000000      0x78787878      0x78787878      0x78787878
  0xdbbc2ae0:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2af0:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b00:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b10:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b20:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b30:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b40:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b50:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b60:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b70:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2b80:     0x78787878      0x78787878      0x00000000      0x78787878
  0xdbbc2b90:     0x78787878      0x78787878      0x78787878      0x78787878
  0xdbbc2ba0:     0x78787878      0x78787878      0x78787878      0x78787878

In the reclaim path, try_to_free_pages() does not setup
sc.target_mem_cgroup and sc is passed to do_try_to_free_pages(), ...,
shrink_node().

In mem_cgroup_iter(), root is set to root_mem_cgroup because
sc->target_mem_cgroup is NULL.  It is possible to assign a memcg to
root_mem_cgroup.nodeinfo.iter in mem_cgroup_iter().

        try_to_free_pages
        	struct scan_control sc = {...}, target_mem_cgroup is 0x0;
        do_try_to_free_pages
        shrink_zones
        shrink_node
        	 mem_cgroup *root = sc->target_mem_cgroup;
        	 memcg = mem_cgroup_iter(root, NULL, &reclaim);
        mem_cgroup_iter()
        	if (!root)
        		root = root_mem_cgroup;
        	...

        	css = css_next_descendant_pre(css, &root->css);
        	memcg = mem_cgroup_from_css(css);
        	cmpxchg(&iter->position, pos, memcg);

My device uses memcg non-hierarchical mode.  When we release a memcg:
invalidate_reclaim_iterators() reaches only dead_memcg and its parents.
If non-hierarchical mode is used, invalidate_reclaim_iterators() never
reaches root_mem_cgroup.

  static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg)
  {
        struct mem_cgroup *memcg = dead_memcg;

        for (; memcg; memcg = parent_mem_cgroup(memcg)
        ...
  }

So the use after free scenario looks like:

  CPU1						CPU2

  try_to_free_pages
  do_try_to_free_pages
  shrink_zones
  shrink_node
  mem_cgroup_iter()
      if (!root)
      	root = root_mem_cgroup;
      ...
      css = css_next_descendant_pre(css, &root->css);
      memcg = mem_cgroup_from_css(css);
      cmpxchg(&iter->position, pos, memcg);

        				invalidate_reclaim_iterators(memcg);
        				...
        				__mem_cgroup_free()
        					kfree(memcg);

  try_to_free_pages
  do_try_to_free_pages
  shrink_zones
  shrink_node
  mem_cgroup_iter()
      if (!root)
      	root = root_mem_cgroup;
      ...
      mz = mem_cgroup_nodeinfo(root, reclaim->pgdat->node_id);
      iter = &mz->iter[reclaim->priority];
      pos = READ_ONCE(iter->position);
      css_tryget(&pos->css) <- use after free

To avoid this, we should also invalidate root_mem_cgroup.nodeinfo.iter
in invalidate_reclaim_iterators().

[cai@lca.pw: fix -Wparentheses compilation warning]
  Link: http://lkml.kernel.org/r/1564580753-17531-1-git-send-email-cai@lca.pw
Link: http://lkml.kernel.org/r/20190730015729.4406-1-miles.chen@mediatek.com
Fixes: 5ac8fb31ad2e ("mm: memcontrol: convert reclaim iterator to simple css refcounting")
Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-08-25 10:50:02 +02:00
..
kasan
kasan: fix shadow_size calculation error in kasan_module_alloc
2018-08-24 13:09:12 +02:00
backing-dev.c
writeback: synchronize sync(2) against cgroup writeback membership switches
2019-03-05 17:58:01 +01:00
balloon_compaction.c
virtio_balloon: fix deadlock on OOM
2018-10-13 09:27:30 +02:00
bootmem.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
cleancache.c
fs: switch ->s_uuid to uuid_t
2017-06-05 16:59:12 +02:00
cma_debug.c
mm/cma_debug.c: fix the break condition in cma_maxchunk_get()
2019-06-15 11:54:51 +02:00
cma.c
mm/cma.c: fail if fixed declaration can't be honored
2019-08-06 19:05:23 +02:00
cma.h
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
compaction.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
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
debug.c
mm: get rid of vmacache_flush_all() entirely
2018-09-19 22:43:48 +02:00
dmapool.c
lib/vsprintf.c: remove %Z support
2017-02-27 18:43:47 -08:00
early_ioremap.c
mm/early_ioremap: Fix boot hang with earlyprintk=efi,keep
2018-02-25 11:08:03 +01:00
fadvise.c
mm/fadvise.c: fix signed overflow UBSAN complaint
2018-09-15 09:45:28 +02:00
failslab.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
filemap.c
mm: add filemap_fdatawait_range_keep_errors()
2019-07-31 07:28:47 +02:00
frame_vector.c
mm/frame_vector.c: release a semaphore in 'get_vaddr_frames()'
2018-03-03 10:24:21 +01:00
frontswap.c
mm, frontswap: convert frontswap_enabled to static key
2016-07-26 16:19:19 -07:00
gup.c
mm/gup.c: remove some BUG_ONs from get_gate_page()
2019-07-31 07:28:56 +02:00
highmem.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
hmm.c
mm, hmm: mark hmm_devmem_{add, add_resource} EXPORT_SYMBOL_GPL
2019-01-13 10:01:02 +01:00
huge_memory.c
mm/huge_memory: fix lockdep complaint on 32-bit i_size_read()
2018-12-05 19:41:08 +01:00
hugetlb_cgroup.c
mm, hugetlb_cgroup: round limit_in_bytes down to hugepage size
2016-05-20 17:58:30 -07:00
hugetlb.c
hugetlbfs: on restore reserve error path retain subpool reservation
2019-06-15 11:54:51 +02:00
hwpoison-inject.c
mm: hwpoison: call shake_page() unconditionally
2017-05-03 15:52:12 -07:00
init-mm.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
internal.h
mm, oom: do not rely on TIF_MEMDIE for memory reserves access
2017-09-06 17:27:30 -07:00
interval_tree.c
lib/interval_tree: fast overlap detection
2017-09-08 18:26:49 -07:00
Kconfig
mm/hmm: select mmu notifier when selecting HMM
2019-06-15 11:54:51 +02:00
Kconfig.debug
kmemcheck: rip it out
2018-02-22 15:42:24 +01:00
khugepaged.c
coredump: fix race condition between collapse_huge_page() and core dumping
2019-06-22 08:16:19 +02:00
kmemleak-test.c
mm: convert printk(KERN_<LEVEL> to pr_<level>
2016-03-17 15:09:34 -07:00
kmemleak.c
mm/kmemleak.c: fix check for softirq context
2019-07-31 07:28:55 +02:00
ksm.c
mm/ksm.c: ignore STABLE_FLAG of rmap_item->address in rmap_walk_ksm()
2018-07-03 11:25:03 +02:00
list_lru.c
mm/list_lru.c: fix memory leak in __memcg_init_list_lru_node
2019-06-19 08:20:54 +02:00
maccess.c
x86: remove more uaccess_32.h complexity
2016-05-22 17:21:27 -07:00
madvise.c
mm: madvise(MADV_DODUMP): allow hugetlbfs pages
2018-10-10 08:54:22 +02:00
Makefile
kmemcheck: rip it out
2018-02-22 15:42:24 +01:00
memblock.c
Revert "mm: page_alloc: skip over regions of invalid pfns where possible"
2018-03-28 18:24:39 +02:00
memcontrol.c
mm/memcontrol.c: fix use after free in mem_cgroup_iter()
2019-08-25 10:50:02 +02:00
memory_hotplug.c
mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone
2019-03-13 14:03:18 -07:00
memory-failure.c
mm: hwpoison: fix thp split handing in soft_offline_in_use_page()
2019-03-23 14:35:24 +01:00
memory.c
mm/memory.c: fix modifying of page protection by insert_pfn()
2019-05-16 19:42:31 +02:00
mempolicy.c
mm/mempolicy.c: fix an incorrect rebind node in mpol_rebind_nodemask
2019-07-03 13:15:59 +02:00
mempool.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
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.c: add missing flush_dcache_page for non-mapped page migrate
2019-04-03 06:25:20 +02:00
mincore.c
mm/mincore.c: make mincore() more conservative
2019-05-21 18:50:16 +02:00
mlock.c
mm/mlock.c: change count_mm_mlocked_page_nr return type
2019-07-10 09:54:36 +02:00
mm_init.c
mm: convert printk(KERN_<LEVEL> to pr_<level>
2016-03-17 15:09:34 -07:00
mmap.c
coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping
2019-04-27 09:35:37 +02:00
mmu_context.c
sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h>
2017-03-02 08:42:38 +01:00
mmu_notifier.c
mm/mmu_notifier: use hlist_add_head_rcu()
2019-07-31 07:28:56 +02:00
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
x86/speculation/l1tf: Disallow non privileged high MMIO PROT_NONE mappings
2018-08-15 18:12:51 +02:00
mremap.c
mremap: properly flush TLB before releasing the page
2018-10-20 09:48:53 +02:00
msync.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
nobootmem.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
Merge branch 'work.set_fs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
2017-09-14 18:13:32 -07:00
oom_kill.c
mm, oom: fix use-after-free in oom_kill_process
2019-02-06 17:31:36 +01:00
page_alloc.c
mem-hotplug: fix node spanned pages when we have a node with only ZONE_MOVABLE
2019-06-15 11:54:51 +02:00
page_counter.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
page_ext.c
mm/page_ext.c: fix an imbalance with kmemleak
2019-04-05 22:31:27 +02:00
page_idle.c
mm/page_idle.c: fix oops because end_pfn is larger than max_pfn
2019-07-03 13:15:59 +02:00
page_io.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
page_isolation.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
page_owner.c
mm/page_owner: fix recursion bug after changing skip entries
2018-05-30 07:52:21 +02:00
page_poison.c
page_poison: play nicely with KASAN
2019-04-05 22:31:28 +02:00
page_vma_mapped.c
mm/rmap: map_pte() was not handling private ZONE_DEVICE page properly
2018-11-13 11:15:08 -08:00
page-writeback.c
mm/page-writeback.c: don't break integrity writeback on ->writepage() error
2019-01-26 09:37:06 +01:00
pagewalk.c
mm/pagewalk.c: report holes in hugetlb ranges
2017-11-24 08:37:04 +01:00
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.
2019-02-12 19:46:05 +01:00
percpu-stats.c
percpu: fix starting offset for chunk statistics traversal
2017-09-27 14:45:57 -07:00
percpu-vm.c
percpu: add __GFP_NORETRY semantics to the percpu balancing path
2018-04-08 14:26:29 +02:00
percpu.c
percpu: do not search past bitmap when allocating an area
2019-06-15 11:54:59 +02:00
pgtable-generic.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
process_vm_access.c
sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h>
2017-03-02 08:42:28 +01:00
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
readahead: stricter check for bdi io_pages
2018-09-09 19:55:53 +02:00
rmap.c
mm: migration: fix migration of huge PMD shared pages
2018-10-13 09:27:22 +02:00
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
tmpfs: fix uninitialized return value in shmem_link
2019-03-23 14:35:17 +01:00
slab_common.c
mm: don't warn about large allocations for slab
2018-12-01 09:42:51 +01:00
slab.c
mm/slab.c: fix an infinite loop in leaks_show()
2019-06-15 11:54:51 +02:00
slab.h
kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK
2018-02-22 15:42:23 +01:00
slob.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
slub.c
slub: make ->cpu_partial unsigned int
2018-10-03 17:00:55 -07:00
sparse-vmemmap.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
sparse.c
mm: sections are not offlined during memory hotremove
2018-05-16 10:10:27 +02:00
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
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
swap_state.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
swap.c
mm: avoid marking swap cached page as lazyfree
2017-10-03 17:54:24 -07:00
swapfile.c
mm/swap: use nr_node_ids for avail_lists in swap_info_struct
2019-01-26 09:37:06 +01:00
truncate.c
mm: cleancache: fix corruption on missed inode invalidation
2018-12-08 13:03:40 +01:00
usercopy.c
mm/usercopy: use memory range to be accessed for wraparound check
2019-08-25 10:50:02 +02:00
userfaultfd.c
hugetlb: use same fault hash key for shared and private mappings
2019-05-31 06:47:12 -07:00
util.c
mm: page_mapped: don't assume compound page is huge or THP
2019-01-16 22:07:11 +01:00
vmacache.c
mm: get rid of vmacache_flush_all() entirely
2018-09-19 22:43:48 +02:00
vmalloc.c
mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()
2019-08-16 10:13:48 +02:00
vmpressure.c
mm, vmpressure: pass-through notification support
2017-07-10 16:32:31 -07:00
vmscan.c
mm: vmscan: scan anonymous pages on file refaults
2019-07-31 07:28:48 +02:00
vmstat.c
mm/vmstat.c: fix /proc/vmstat format for CONFIG_DEBUG_TLBFLUSH=y CONFIG_SMP=n
2019-04-27 09:35:41 +02:00
workingset.c
License cleanup: add SPDX GPL-2.0 license identifier to files with no license
2017-11-02 11:10:55 +01:00
z3fold.c
z3fold: fix possible reclaim races
2018-12-01 09:42:54 +01:00
zbud.c
…
zpool.c
…
zsmalloc.c
zsmalloc: calling zs_map_object() from irq is a bug
2017-12-14 09:53:10 +01:00
zswap.c
zswap: re-check zswap_is_full() after do zswap_shrink()
2018-09-05 09:26:30 +02:00