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Eric Biggers 263630e8d1 mm/madvise.c: fix freeing of locked page with MADV_FREE 
If madvise(..., MADV_FREE) split a transparent hugepage, it called
put_page() before unlock_page().

This was wrong because put_page() can free the page, e.g. if a
concurrent madvise(..., MADV_DONTNEED) has removed it from the memory
mapping. put_page() then rightfully complained about freeing a locked
page.

Fix this by moving the unlock_page() before put_page().

This bug was found by syzkaller, which encountered the following splat:

    BUG: Bad page state in process syzkaller412798  pfn:1bd800
    page:ffffea0006f60000 count:0 mapcount:0 mapping:          (null) index:0x20a00
    flags: 0x200000000040019(locked|uptodate|dirty|swapbacked)
    raw: 0200000000040019 0000000000000000 0000000000020a00 00000000ffffffff
    raw: ffffea0006f60020 ffffea0006f60020 0000000000000000 0000000000000000
    page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
    bad because of flags: 0x1(locked)
    Modules linked in:
    CPU: 1 PID: 3037 Comm: syzkaller412798 Not tainted 4.13.0-rc5+ #35
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
     __dump_stack lib/dump_stack.c:16 [inline]
     dump_stack+0x194/0x257 lib/dump_stack.c:52
     bad_page+0x230/0x2b0 mm/page_alloc.c:565
     free_pages_check_bad+0x1f0/0x2e0 mm/page_alloc.c:943
     free_pages_check mm/page_alloc.c:952 [inline]
     free_pages_prepare mm/page_alloc.c:1043 [inline]
     free_pcp_prepare mm/page_alloc.c:1068 [inline]
     free_hot_cold_page+0x8cf/0x12b0 mm/page_alloc.c:2584
     __put_single_page mm/swap.c:79 [inline]
     __put_page+0xfb/0x160 mm/swap.c:113
     put_page include/linux/mm.h:814 [inline]
     madvise_free_pte_range+0x137a/0x1ec0 mm/madvise.c:371
     walk_pmd_range mm/pagewalk.c:50 [inline]
     walk_pud_range mm/pagewalk.c:108 [inline]
     walk_p4d_range mm/pagewalk.c:134 [inline]
     walk_pgd_range mm/pagewalk.c:160 [inline]
     __walk_page_range+0xc3a/0x1450 mm/pagewalk.c:249
     walk_page_range+0x200/0x470 mm/pagewalk.c:326
     madvise_free_page_range.isra.9+0x17d/0x230 mm/madvise.c:444
     madvise_free_single_vma+0x353/0x580 mm/madvise.c:471
     madvise_dontneed_free mm/madvise.c:555 [inline]
     madvise_vma mm/madvise.c:664 [inline]
     SYSC_madvise mm/madvise.c:832 [inline]
     SyS_madvise+0x7d3/0x13c0 mm/madvise.c:760
     entry_SYSCALL_64_fastpath+0x1f/0xbe

Here is a C reproducer:

    #define _GNU_SOURCE
    #include <pthread.h>
    #include <sys/mman.h>
    #include <unistd.h>

    #define MADV_FREE	8
    #define PAGE_SIZE	4096

    static void *mapping;
    static const size_t mapping_size = 0x1000000;

    static void *madvise_thrproc(void *arg)
    {
        madvise(mapping, mapping_size, (long)arg);
    }

    int main(void)
    {
        pthread_t t[2];

        for (;;) {
            mapping = mmap(NULL, mapping_size, PROT_WRITE,
                           MAP_POPULATE|MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);

            munmap(mapping + mapping_size / 2, PAGE_SIZE);

            pthread_create(&t[0], 0, madvise_thrproc, (void*)MADV_DONTNEED);
            pthread_create(&t[1], 0, madvise_thrproc, (void*)MADV_FREE);
            pthread_join(t[0], NULL);
            pthread_join(t[1], NULL);
            munmap(mapping, mapping_size);
        }
    }

Note: to see the splat, CONFIG_TRANSPARENT_HUGEPAGE=y and
CONFIG_DEBUG_VM=y are needed.

Google Bug Id: 64696096

Link: http://lkml.kernel.org/r/20170823205235.132061-1-ebiggers3@gmail.com
Fixes: 854e9ed09d ("mm: support madvise(MADV_FREE)")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>	[v4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2017-08-25 16:12:46 -07:00
..
kasan kasan: avoid -Wmaybe-uninitialized warning 2017-08-02 16:34:46 -07:00
Kconfig mm/kasan: add support for memory hotplug 2017-07-10 16:32:33 -07:00
Kconfig.debug mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
Makefile percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
backing-dev.c bdi: Drop 'parent' argument from bdi_register[_va]() 2017-04-20 12:09:55 -06:00
balloon_compaction.c mm/balloon_compaction.c: don't zero ballooned pages 2017-08-10 15:54:07 -07:00
bootmem.c
…
cleancache.c fs: switch ->s_uuid to uuid_t 2017-06-05 16:59:12 +02:00
cma.c cma: fix calculation of aligned offset 2017-07-10 16:32:32 -07:00
cma.h cma: Store a name in the cma structure 2017-04-18 20:41:12 +02:00
cma_debug.c mm/cma_debug.c: fix stack corruption due to sprintf usage 2017-08-18 15:32:02 -07:00
compaction.c mm, compaction: skip over holes in __reset_isolation_suitable 2017-07-06 16:24:32 -07:00
debug.c mm: make tlb_flush_pending global 2017-08-10 15:54:07 -07:00
debug_page_ref.c
…
dmapool.c
…
early_ioremap.c
…
fadvise.c
…
failslab.c
…
filemap.c mm: hugetlb: return immediately for hugetlb page in __delete_from_page_cache() 2017-07-10 16:32:30 -07:00
frame_vector.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
frontswap.c
…
gup.c mm, gup: ensure real head page is ref-counted when using hugepages 2017-07-06 16:24:34 -07:00
highmem.c
…
huge_memory.c mm, oom: fix potential data corruption when oom_reaper races with writer 2017-08-18 15:32:01 -07:00
hugetlb.c userfaultfd: hugetlbfs: remove superfluous page unlock in VM_SHARED case 2017-08-10 15:54:06 -07:00
hugetlb_cgroup.c
…
hwpoison-inject.c mm: hwpoison: call shake_page() unconditionally 2017-05-03 15:52:12 -07:00
init-mm.c
…
internal.h mm, mprotect: flush TLB if potentially racing with a parallel reclaim leaving stale TLB entries 2017-08-02 16:34:46 -07:00
interval_tree.c
…
khugepaged.c mm: make PR_SET_THP_DISABLE immediately active 2017-07-10 16:32:31 -07:00
kmemcheck.c mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU 2017-04-18 11:42:36 -07:00
kmemleak-test.c
…
kmemleak.c mm: kmemleak: treat vm_struct as alternative reference to vmalloc'ed objects 2017-07-06 16:24:34 -07:00
ksm.c mm: fix KSM data corruption 2017-08-10 15:54:07 -07:00
list_lru.c mm/list_lru.c: fix list_lru_count_node() to be race free 2017-07-10 16:32:33 -07:00
maccess.c
…
madvise.c mm/madvise.c: fix freeing of locked page with MADV_FREE 2017-08-25 16:12:46 -07:00
memblock.c mm: discard memblock data later 2017-08-18 15:32:01 -07:00
memcontrol.c mm: memcontrol: fix NULL pointer crash in test_clear_page_writeback() 2017-08-18 15:32:01 -07:00
memory-failure.c mm, hugetlb, soft_offline: use new_page_nodemask for soft offline migration 2017-07-10 16:32:32 -07:00
memory.c mm, oom: fix potential data corruption when oom_reaper races with writer 2017-08-18 15:32:01 -07:00
memory_hotplug.c mm/memory-hotplug: switch locking to a percpu rwsem 2017-07-10 16:32:33 -07:00
mempolicy.c mm/mempolicy: fix use after free when calling get_mempolicy 2017-08-18 15:32:02 -07:00
mempool.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
memtest.c
…
migrate.c Sanitize 'move_pages()' permission checks 2017-08-20 13:26:27 -07:00
mincore.c
…
mlock.c mlock: fix mlock count can not decrease in race condition 2017-06-02 15:07:38 -07:00
mm_init.c
…
mmap.c mm: fix overflow check in expand_upwards() 2017-07-14 15:05:12 -07:00
mmu_context.c
…
mmu_notifier.c mm: Use static initialization for "srcu" 2017-04-18 11:38:22 -07:00
mmzone.c
…
mprotect.c mm: migrate: prevent racy access to tlb_flush_pending 2017-08-10 15:54:07 -07:00
mremap.c userfaultfd: non-cooperative: notify about unmap of destination during mremap 2017-08-02 16:34:46 -07:00
msync.c
…
nobootmem.c mm: discard memblock data later 2017-08-18 15:32:01 -07:00
nommu.c mm, vmalloc: use __GFP_HIGHMEM implicitly 2017-05-08 17:15:13 -07:00
oom_kill.c mm/oom_kill.c: add tracepoints for oom reaper-related events 2017-07-10 16:32:32 -07:00
page-writeback.c mm: memcontrol: fix NULL pointer crash in test_clear_page_writeback() 2017-08-18 15:32:01 -07:00
page_alloc.c PM/hibernate: touch NMI watchdog when creating snapshot 2017-08-25 16:12:46 -07:00
page_counter.c
…
page_ext.c mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
page_idle.c mm: make rmap_one boolean function 2017-05-03 15:52:10 -07:00
page_io.c mm/page_io.c: fix oops during block io poll in swapin path 2017-08-02 17:16:11 -07:00
page_isolation.c mm: unify new_node_page and alloc_migrate_target 2017-07-10 16:32:31 -07:00
page_owner.c mm: avoid taking zone lock in pagetypeinfo_showmixed() 2017-07-10 16:32:32 -07:00
page_poison.c mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
page_vma_mapped.c mm/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
pagewalk.c mm/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
percpu-internal.h percpu: fix early calls for spinlock in pcpu_stats 2017-06-21 13:53:52 -04:00
percpu-km.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu-stats.c percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
percpu-vm.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu.c percpu: resolve err may not be initialized in pcpu_alloc 2017-06-21 12:00:45 -04:00
pgtable-generic.c
…
process_vm_access.c
…
quicklist.c
…
readahead.c
…
rmap.c rmap: do not call mmu_notifier_invalidate_page() under ptl 2017-08-10 15:54:07 -07:00
rodata_test.c mm: remove rodata_test_data export, add pr_fmt 2017-05-03 15:52:09 -07:00
shmem.c mm, shmem: fix handling /sys/kernel/mm/transparent_hugepage/shmem_enabled 2017-08-25 16:12:46 -07:00
slab.c mm: memcontrol: account slab stats per lruvec 2017-07-06 16:24:35 -07:00
slab.h mm: memcontrol: account slab stats per lruvec 2017-07-06 16:24:35 -07:00
slab_common.c mm: allow slab_nomerge to be set at build time 2017-07-06 16:24:31 -07:00
slob.c mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU 2017-04-18 11:42:36 -07:00
slub.c slub: fix per memcg cache leak on css offline 2017-08-18 15:32:01 -07:00
sparse-vmemmap.c mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful semantic 2017-07-12 16:26:03 -07:00
sparse.c mm, memory_hotplug: do not associate hotadded memory to zones until online 2017-07-06 16:24:32 -07:00
swap.c mm: swap: provide lru_add_drain_all_cpuslocked() 2017-07-10 16:32:33 -07:00
swap_cgroup.c mm, THP, swap: delay splitting THP during swap out 2017-07-06 16:24:31 -07:00
swap_slots.c mm/swap_slots.c: don't disable preemption while taking the per-CPU cache 2017-07-10 16:32:32 -07:00
swap_state.c swap: add block io poll in swapin path 2017-07-10 16:32:30 -07:00
swapfile.c swap: add block io poll in swapin path 2017-07-10 16:32:30 -07:00
truncate.c mm/truncate.c: fix THP handling in invalidate_mapping_pages() 2017-07-10 16:32:32 -07:00
usercopy.c
…
userfaultfd.c
…
util.c mm: fix global NR_SLAB_.*CLAIMABLE counter reads 2017-08-10 15:54:06 -07:00
vmacache.c
…
vmalloc.c mm/vmalloc.c: don't unconditonally use __GFP_HIGHMEM 2017-08-18 15:32:02 -07:00
vmpressure.c mm, vmpressure: pass-through notification support 2017-07-10 16:32:31 -07:00
vmscan.c mm, tree wide: replace __GFP_REPEAT by __GFP_RETRY_MAYFAIL with more useful semantic 2017-07-12 16:26:03 -07:00
vmstat.c mm: avoid taking zone lock in pagetypeinfo_showmixed() 2017-07-10 16:32:32 -07:00
workingset.c mm: memcontrol: per-lruvec stats infrastructure 2017-07-06 16:24:35 -07:00
z3fold.c z3fold: fix page locking in z3fold_alloc() 2017-04-13 18:24:20 -07:00
zbud.c
…
zpool.c
…
zsmalloc.c zram: do not free pool->size_class 2017-08-02 16:34:47 -07:00
zswap.c mm/zswap.c: delete an error message for a failed memory allocation in zswap_dstmem_prepare() 2017-07-06 16:24:35 -07:00