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Message-Id: <20211116235733.3774702-1-almasrymina@google.com>
Date: Tue, 16 Nov 2021 15:57:32 -0800
From: Mina Almasry <almasrymina@...gle.com>
To: Mike Kravetz <mike.kravetz@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Mina Almasry <almasrymina@...gle.com>, Wei Xu <weixugc@...gle.com>,
James Houghton <jthoughton@...gle.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v1] hugetlb, userfaultfd: Fix reservation restore on
userfaultfd error
Currently in the is_continue case in hugetlb_mcopy_atomic_pte(), if we
bail out using "goto out_release_unlock;" in the cases where idx >=
size, or !huge_pte_none(), the code will detect that new_pagecache_page
== false, and so call restore_reserve_on_error().
In this case I see restore_reserve_on_error() delete the reservation,
and the following call to remove_inode_hugepages() will increment
h->resv_hugepages causing a 100% reproducible leak.
We should treat the is_continue case similar to adding a page into the
pagecache and set new_pagecache_page to true, to indicate that there is
no reservation to restore on the error path, and we need not call
restore_reserve_on_error().
Cc: Wei Xu <weixugc@...gle.com>
Fixes: c7b1850dfb41 ("hugetlb: don't pass page cache pages to restore_reserve_on_error")
Signed-off-by: Mina Almasry <almasrymina@...gle.com>
Reported-by: James Houghton <jthoughton@...gle.com>
---
mm/hugetlb.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e09159c957e3..25a7a3d84607 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5741,6 +5741,14 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
page = find_lock_page(mapping, idx);
if (!page)
goto out;
+ /*
+ * Set new_pagecache_page to true, as we've added a page to the
+ * pagecache, but userfaultfd hasn't set up a mapping for this
+ * page yet. If we bail out before setting up the mapping, we
+ * want to indicate to restore_reserve_on_error() that we've
+ * added the page to the page cache.
+ */
+ new_pagecache_page = true;
} else if (!*pagep) {
/* If a page already exists, then it's UFFDIO_COPY for
* a non-missing case. Return -EEXIST.
--
2.34.0.rc1.387.gb447b232ab-goog
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