From: Jann Horn <jannh@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org, "Jason Gunthorpe" <jgg@ziepe.ca>,
"John Hubbard" <jhubbard@nvidia.com>,
"Christoph Hellwig" <hch@lst.de>,
linux-kernel@vger.kernel.org,
"Christian König" <christian.koenig@amd.com>
Subject: [PATCH] mm/mmu_notifier: Fix mmget() assert in __mmu_interval_notifier_insert
Date: Tue, 1 Sep 2020 02:01:43 +0200 [thread overview]
Message-ID: <20200901000143.207585-1-jannh@google.com> (raw)
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
next reply other threads:[~2020-09-01 0:02 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 0:01 Jann Horn [this message]
2020-09-01 0:26 ` [PATCH] mm/mmu_notifier: Fix mmget() assert in __mmu_interval_notifier_insert Jason Gunthorpe
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