The patch titled
Subject: userfaultfd: shmem: avoid a lockup resulting from corrupted page->flags
has been added to the -mm tree. Its filename is
userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Subject: userfaultfd: shmem: avoid a lockup resulting from corrupted page->flags
Use the non atomic version of __SetPageUptodate while the page is still
private and not visible to lookup operations. Using the non atomic
version after the page is already visible to lookups is unsafe as there
would be concurrent lock_page operation modifying the page->flags while it
runs.
This solves a lockup in find_lock_entry with the userfaultfd_shmem
selftest.
userfaultfd_shm D14296 691 1 0x00000004
Call Trace:
? __schedule+0x311/0xb60
schedule+0x3d/0x90
schedule_timeout+0x228/0x420
? mark_held_locks+0x71/0x90
? ktime_get+0x134/0x170
? kvm_clock_read+0x25/0x30
? kvm_clock_get_cycles+0x9/0x10
? ktime_get+0xd6/0x170
? __delayacct_blkio_start+0x1f/0x30
io_schedule_timeout+0xa4/0x110
? trace_hardirqs_on+0xd/0x10
__lock_page+0x12d/0x170
? add_to_page_cache_lru+0xe0/0xe0
find_lock_entry+0xa4/0x190
shmem_getpage_gfp+0xb9/0xc30
? alloc_set_pte+0x56e/0x610
? radix_tree_next_chunk+0xf6/0x2d0
shmem_fault+0x70/0x1c0
? filemap_map_pages+0x3bd/0x530
__do_fault+0x21/0x150
handle_mm_fault+0xec9/0x1490
__do_page_fault+0x20d/0x520
trace_do_page_fault+0x61/0x270
do_async_page_fault+0x19/0x80
async_page_fault+0x25/0x30
Link: http://lkml.kernel.org/r/20170116180408.12184-2-aarcange@xxxxxxxxxx
Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reported-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff -puN mm/shmem.c~userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags mm/shmem.c
--- a/mm/shmem.c~userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags
+++ a/mm/shmem.c
@@ -2241,6 +2241,7 @@ int shmem_mcopy_atomic_pte(struct mm_str
VM_BUG_ON(PageLocked(page) || PageSwapBacked(page));
__SetPageLocked(page);
__SetPageSwapBacked(page);
+ __SetPageUptodate(page);
ret = mem_cgroup_try_charge(page, dst_mm, gfp, &memcg, false);
if (ret)
@@ -2265,8 +2266,6 @@ int shmem_mcopy_atomic_pte(struct mm_str
if (!pte_none(*dst_pte))
goto out_release_uncharge_unlock;
- __SetPageUptodate(page);
-
lru_cache_add_anon(page);
spin_lock(&info->lock);
_
Patches currently in -mm which might be from aarcange@xxxxxxxxxx are
userfaultfd-fix-sigbus-resulting-from-false-rwsem-wakeups.patch
userfaultfd-document-_ior-_iow.patch
userfaultfd-correct-comment-about-uffd_feature_pagefault_flag_wp.patch
userfaultfd-convert-bug-to-warn_on_once.patch
userfaultfd-use-vma_is_anonymous.patch
userfaultfd-non-cooperative-report-all-available-features-to-userland.patch
userfaultfd-non-cooperative-add-fork-event-build-warning-fix.patch
userfaultfd-non-cooperative-optimize-mremap_userfaultfd_complete.patch
userfaultfd-non-cooperative-avoid-madv_dontneed-race-condition.patch
userfaultfd-non-cooperative-wake-userfaults-after-uffdio_unregister.patch
userfaultfd-hugetlbfs-gup-support-vm_fault_retry.patch
userfaultfd-hugetlbfs-uffd_feature_missing_hugetlbfs.patch
userfaultfd-shmem-add-tlbflushh-header-for-microblaze.patch
userfaultfd-shmem-lock-the-page-before-adding-it-to-pagecache.patch
userfaultfd-shmem-avoid-a-lockup-resulting-from-corrupted-page-flags.patch
userfaultfd-shmem-avoid-leaking-blocks-and-used-blocks-in-uffdio_copy.patch
userfaultfd-hugetlbfs-uffd_feature_missing_shmem.patch
userfaultfd-selftest-test-uffdio_zeropage-on-all-memory-types.patch
mm-mprotect-use-pmd_trans_unstable-instead-of-taking-the-pmd_lock.patch
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