From 83c8f7b5e194eaf3fb268c513e23e23e892de8ed Mon Sep 17 00:00:00 2001 From: Joshua Hahn Date: Mon, 1 Dec 2025 10:07:38 -0800 Subject: [PATCH] mm/mm_init: Introduce a boot parameter for check_pages Use-after-free and double-free bugs can be very difficult to track down. The kernel is good at tracking these and preventing bad pages from being used/created through simple checks gated behind "check_pages_enabled". Currently, the only ways to enable this flag is by building with CONFIG_DEBUG_VM, or as a side effect of other checks such as init_on_{alloc, free}, page_poisoning, or debug_pagealloc among others. These solutions are powerful, but may often be too coarse in balancing the performance vs. safety that a user may want, particularly in latency-sensitive production environments. Introduce a new boot parameter "check_pages", which enables page checking with no other side effects. It takes kstrbool-able inputs as an argument (i.e. 0/1, true/false, on/off, ...). This patch is backwards-compatible; setting CONFIG_DEBUG_VM still enables page checking. Acked-by: SeongJae Park Acked-by: Michal Hocko Acked-by: Vlastimil Babka Reviewed-by: Anshuman Khandual Signed-off-by: Joshua Hahn Link: https://patch.msgid.link/20251201180739.2330474-1-joshua.hahnjy@gmail.com Signed-off-by: Mike Rapoport (Microsoft) --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ mm/mm_init.c | 10 +++++++++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e5..acdc7fbdecacf 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -669,6 +669,14 @@ nokmem -- Disable kernel memory accounting. nobpf -- Disable BPF memory accounting. + check_pages= [MM,EARLY] Enable sanity checking of pages after + allocations / before freeing. This adds checks to catch + double-frees, use-after-frees, and other sources of + page corruption by inspecting page internals (flags, + mapcount/refcount, memcg_data, etc.). + Format: { "0" | "1" } + Default: 0 (1 if CONFIG_DEBUG_VM is set) + checkreqprot= [SELINUX] Set initial checkreqprot flag value. Format: { "0" | "1" } See security/selinux/Kconfig help text. diff --git a/mm/mm_init.c b/mm/mm_init.c index 7712d887b6963..220b7c6b5fb2c 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -2525,6 +2525,14 @@ early_param("init_on_free", early_init_on_free); DEFINE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled); +static bool check_pages_enabled_early __initdata; + +static int __init early_check_pages(char *buf) +{ + return kstrtobool(buf, &check_pages_enabled_early); +} +early_param("check_pages", early_check_pages); + /* * Enable static keys related to various memory debugging and hardening options. * Some override others, and depend on early params that are evaluated in the @@ -2534,7 +2542,7 @@ DEFINE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled); static void __init mem_debugging_and_hardening_init(void) { bool page_poisoning_requested = false; - bool want_check_pages = false; + bool want_check_pages = check_pages_enabled_early; #ifdef CONFIG_PAGE_POISONING /* -- 2.47.3