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    Subject[PATCH v8 4/8] mm, arm64: untag user addresses in mm/gup.c
    Date
    mm/gup.c provides a kernel interface that accepts user addresses and
    manipulates user pages directly (for example get_user_pages, that is used
    by the futex syscall). Since a user can provided tagged addresses, we need
    to handle such case.

    Add untagging to gup.c functions that use user addresses for vma lookup.

    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    ---
    mm/gup.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/mm/gup.c b/mm/gup.c
    index f76e77a2d34b..6ff310818616 100644
    --- a/mm/gup.c
    +++ b/mm/gup.c
    @@ -677,6 +677,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
    if (!nr_pages)
    return 0;

    + start = untagged_addr(start);
    +
    VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));

    /*
    @@ -840,6 +842,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
    struct vm_area_struct *vma;
    vm_fault_t ret, major = 0;

    + address = untagged_addr(address);
    +
    if (unlocked)
    fault_flags |= FAULT_FLAG_ALLOW_RETRY;

    --
    2.19.1.930.g4563a0d9d0-goog
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