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mm: page table check

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Check user page table entries at the time they are added and removed.

Allows to synchronously catch memory corruption issues related to double
mapping.

When a pte for an anonymous page is added into page table, we verify
that this pte does not already point to a file backed page, and vice
versa if this is a file backed page that is being added we verify that
this page does not have an anonymous mapping

We also enforce that read-only sharing for anonymous pages is allowed
(i.e.  cow after fork).  All other sharing must be for file pages.

Page table check allows to protect and debug cases where "struct page"
metadata became corrupted for some reason.  For example, when refcnt or
mapcount become invalid.

Link: https://lkml.kernel.org/r/20211221154650.1047963-4-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sami Tolvanen <samitolvanen@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Xu <weixugc@google.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Pasha Tatashin
2022-01-15 16:30:28 +02:00
committed by Linus Torvalds
parent 08d5b29eac
commit df4e817b71
10 changed files with 519 additions and 0 deletions
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mm/Kconfig.debug
+24
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@@ -62,6 +62,30 @@ config PAGE_OWNER
If unsure, say N.
config PAGE_TABLE_CHECK
bool "Check for invalid mappings in user page tables"
depends on ARCH_SUPPORTS_PAGE_TABLE_CHECK
select PAGE_EXTENSION
help
Check that anonymous page is not being mapped twice with read write
permissions. Check that anonymous and file pages are not being
erroneously shared. Since the checking is performed at the time
entries are added and removed to user page tables, leaking, corruption
and double mapping problems are detected synchronously.
If unsure say "n".
config PAGE_TABLE_CHECK_ENFORCED
bool "Enforce the page table checking by default"
depends on PAGE_TABLE_CHECK
help
Always enable page table checking. By default the page table checking
is disabled, and can be optionally enabled via page_table_check=on
kernel parameter. This config enforces that page table check is always
enabled.
If unsure say "n".
config PAGE_POISONING
bool "Poison pages after freeing"
help