From: Pasha Tatashin <pasha.tatashin@soleen.com>
To: pasha.tatashin@soleen.com, akpm@linux-foundation.org,
corbet@lwn.net, linux-mm@kvack.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com
Subject: [PATCH 1/3] mm/page_table_check: Check writable zero page in page table check
Date: Sun, 11 Sep 2022 09:59:21 +0000 [thread overview]
Message-ID: <20220911095923.3614387-2-pasha.tatashin@soleen.com> (raw)
In-Reply-To: <20220911095923.3614387-1-pasha.tatashin@soleen.com>
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
The zero page should remain all zero, so that it can be mapped as
read-only for read faults of memory that should be zeroed. If it is ever
mapped writable to userspace, it could become non-zero and so other apps
would unexpectedly get non-zero data. So the zero page should never be
mapped writable to userspace. Check for this condition in
page_table_check_set().
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
mm/page_table_check.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/page_table_check.c b/mm/page_table_check.c
index e2062748791a..665ece0d55d4 100644
--- a/mm/page_table_check.c
+++ b/mm/page_table_check.c
@@ -102,6 +102,8 @@ static void page_table_check_set(struct mm_struct *mm, unsigned long addr,
if (!pfn_valid(pfn))
return;
+ BUG_ON(is_zero_pfn(pfn) && rw);
+
page = pfn_to_page(pfn);
page_ext = lookup_page_ext(page);
anon = PageAnon(page);
--
2.37.2.789.g6183377224-goog
next prev parent reply other threads:[~2022-09-11 10:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-11 9:59 [PATCH 0/3] page table check default to warn instead of panic Pasha Tatashin
2022-09-11 9:59 ` Pasha Tatashin [this message]
2022-09-12 15:58 ` [PATCH 1/3] mm/page_table_check: Check writable zero page in page table check Edgecombe, Rick P
2022-09-26 8:26 ` David Hildenbrand
2022-09-11 9:59 ` [PATCH 2/3] mm/page_table_check: Do WARN_ON instead of BUG_ON by default Pasha Tatashin
2022-09-11 16:08 ` Matthew Wilcox
2022-09-11 20:42 ` Pasha Tatashin
2022-09-26 8:28 ` David Hildenbrand
2022-09-26 1:16 ` [mm/page_table_check] 6e807506f4: WARNING:at_mm/page_table_check.c:#page_table_check_set kernel test robot
2022-09-26 1:16 ` kernel test robot
2022-09-11 9:59 ` [PATCH 3/3] doc/vm: add information about page_table_check=panic Pasha Tatashin
2022-09-12 20:23 ` [PATCH 0/3] page table check default to warn instead of panic Andrew Morton
2022-09-20 18:11 ` Pasha Tatashin
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