lkml.org 
[lkml]   [2020]   [Aug]   [31]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    Subject[PATCH] mm/mmu_notifier: Fix mmget() assert in __mmu_interval_notifier_insert
    From
    The comment talks about having to hold mmget() (which means mm_users), but
    the actual check is on mm_count (which would be mmgrab()).

    Given that MMU notifiers are torn down in
    mmput() -> __mmput() -> exit_mmap() -> mmu_notifier_release(),
    I believe that the comment is correct and the check should be on
    mm->mm_users. Fix it up accordingly.

    Fixes: 99cb252f5e68 ("mm/mmu_notifier: add an interval tree notifier")
    Signed-off-by: Jann Horn <jannh@google.com>
    ---
    Can someone please double-check this? I'm like 90% sure that I fixed
    this the right way around, but it'd be good if someone more familiar
    with mmu notifiers could confirm.

    mm/mmu_notifier.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
    index 4fc918163dd3..5654dd19addc 100644
    --- a/mm/mmu_notifier.c
    +++ b/mm/mmu_notifier.c
    @@ -913,7 +913,7 @@ static int __mmu_interval_notifier_insert(
    return -EOVERFLOW;

    /* Must call with a mmget() held */
    - if (WARN_ON(atomic_read(&mm->mm_count) <= 0))
    + if (WARN_ON(atomic_read(&mm->mm_users) <= 0))
    return -EINVAL;

    /* pairs with mmdrop in mmu_interval_notifier_remove() */
    base-commit: 15bc20c6af4ceee97a1f90b43c0e386643c071b4
    --
    2.28.0.402.g5ffc5be6b7-goog

    \
     
     \ /
      Last update: 2020-09-01 02:03    [W:3.256 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site