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[058/156] mm/mmu_notifier: fix mmget() assert in __mmu_interval_notifier_insert

Message ID 20201016024431.w2DQBMSrK%akpm@linux-foundation.org
State New
Headers show
Series [001/156] device-dax/kmem: fix resource release | expand

Commit Message

Andrew Morton Oct. 16, 2020, 2:44 a.m. UTC
From: Jann Horn <jannh@google.com>
Subject: 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.

Link: https://lkml.kernel.org/r/20200901000143.207585-1-jannh@google.com
Fixes: 99cb252f5e68 ("mm/mmu_notifier: add an interval tree notifier")
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christian K├Ânig <christian.koenig@amd.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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


--- a/mm/mmu_notifier.c~mm-mmu_notifier-fix-mmget-assert-in-__mmu_interval_notifier_insert
+++ a/mm/mmu_notifier.c
@@ -913,7 +913,7 @@  static int __mmu_interval_notifier_inser
 		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() */