This new config option will sanitize all freed pages. This is a pretty low-level change useful to track some cases of use-after-free, help kernel same-page merging in VM environments, and counter a few info leaks. Signed-off-by: Anisse Astier <anisse@xxxxxxxxx> --- mm/Kconfig | 12 ++++++++++++ mm/page_alloc.c | 5 +++++ 2 files changed, 17 insertions(+) diff --git a/mm/Kconfig b/mm/Kconfig index 390214d..cb2df5f 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -635,3 +635,15 @@ config MAX_STACK_SIZE_MB changed to a smaller value in which case that is used. A sane initial value is 80 MB. + +config SANITIZE_FREED_PAGES + bool "Sanitize memory pages after free" + default n + help + This option is used to make sure all pages freed are zeroed. This is + quite low-level and doesn't handle your slab buffers. + It has various applications, from preventing some info leaks to + helping kernel same-page merging in virtualised environments. + Depending on your workload, it will reduce performance of about 3%. + + If unsure, say N. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 05fcec9..c71440a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -803,6 +803,11 @@ static bool free_pages_prepare(struct page *page, unsigned int order) debug_check_no_obj_freed(page_address(page), PAGE_SIZE << order); } + +#ifdef CONFIG_SANITIZE_FREED_PAGES + zero_pages(page, order); +#endif + arch_free_page(page, order); kernel_map_pages(page, 1 << order, 0); -- 1.9.3 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>