On 23. 11. 21, 22:48, Pasha Tatashin wrote:
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.
Signed-off-by: Pasha Tatashin <pasha.tatashin@xxxxxxxxxx>
...
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -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 defauled"
s/defauled/default/
regards,
--
js
suse labs
