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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. Signed-off-by: Joshua Hahn --- v1 --> v2: - Changed check_pages from a build config into a boot config, as suggested by Vlastimil. - Introduced the second patch, which decouples page checking from init_on_page_alloc and init_on_page_free. --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ mm/mm_init.c | 11 ++++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6c42061ca20e..0ba9561440a7 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 c6812b4dbb2e..01d46efc42b4 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 @@ -2591,7 +2599,8 @@ static void __init mem_debugging_and_hardening_init(void) * of struct pages being allocated or freed. With CONFIG_DEBUG_VM it's * enabled already. */ - if (!IS_ENABLED(CONFIG_DEBUG_VM) && want_check_pages) + if (!IS_ENABLED(CONFIG_DEBUG_VM) && (_check_pages_enabled_early || + want_check_pages)) static_branch_enable(&check_pages_enabled); } -- 2.47.3