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mm/mmu_notifier: fix mmget() assert in __mmu_interval_notifier_insert 

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: 99cb252f5e ("mm/mmu_notifier: add an interval tree notifier")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christian König <christian.koenig@amd.com
Link: https://lkml.kernel.org/r/20200901000143.207585-1-jannh@google.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
zero-sugar-mainline-defconfig
Jann Horn 2020-10-15 20:07:43 -07:00 committed by Linus Torvalds
parent 295a173023
commit c9682d1027
1 changed files with 1 additions and 1 deletions
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mm/mmu_notifier.c
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@ -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() */