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mm/mm_init: Introduce a boot parameter for check_pages

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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 <sj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Link: https://patch.msgid.link/20251201180739.2330474-1-joshua.hahnjy@gmail.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
This commit is contained in:
Joshua Hahn
2025-12-01 10:07:38 -08:00
committed by Mike Rapoport (Microsoft)
parent ac3fd01e4c
commit 83c8f7b5e1
2 changed files with 17 additions and 1 deletions
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8
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -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.

10
mm/mm_init.c
View File

@@ -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
/*