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| author | Mina Almasry <almasrymina@google.com> | 2021-06-30 18:48:19 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-30 20:47:26 -0700 |
| commit | 8cc5fcbb5be814c115085549b700e473685b11e9 (patch) | |
| tree | cb4b0dc98bed2f3d51ca2b5dd2026bfb09bdca9c /mm/migrate.c | |
| parent | 22f3c951865be13dd32ba042b50bea3f6f93e115 (diff) | |
| download | linux-8cc5fcbb5be814c115085549b700e473685b11e9.tar.bz2 | |
mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY
On UFFDIO_COPY, if we fail to copy the page contents while holding the
hugetlb_fault_mutex, we will drop the mutex and return to the caller after
allocating a page that consumed a reservation. In this case there may be
a fault that double consumes the reservation. To handle this, we free the
allocated page, fix the reservations, and allocate a temporary hugetlb
page and return that to the caller. When the caller does the copy outside
of the lock, we again check the cache, and allocate a page consuming the
reservation, and copy over the contents.
Test:
Hacked the code locally such that resv_huge_pages underflows produce
a warning and the copy_huge_page_from_user() always fails, then:
./tools/testing/selftests/vm/userfaultfd hugetlb_shared 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
./tools/testing/selftests/vm/userfaultfd hugetlb 10
2 /tmp/kokonut_test/huge/userfaultfd_test && echo test success
Both tests succeed and produce no warnings. After the
test runs number of free/resv hugepages is correct.
[yuehaibing@huawei.com: remove set but not used variable 'vm_alloc_shared']
Link: https://lkml.kernel.org/r/20210601141610.28332-1-yuehaibing@huawei.com
[almasrymina@google.com: fix allocation error check and copy func name]
Link: https://lkml.kernel.org/r/20210605010626.1459873-1-almasrymina@google.com
Link: https://lkml.kernel.org/r/20210528005029.88088-1-almasrymina@google.com
Signed-off-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
| -rw-r--r-- | mm/migrate.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 75a15f0a2698..8fc766e52e52 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -553,7 +553,7 @@ static void __copy_gigantic_page(struct page *dst, struct page *src, } } -static void copy_huge_page(struct page *dst, struct page *src) +void copy_huge_page(struct page *dst, struct page *src) { int i; int nr_pages; |