[PATCH v2 1/3] lockdown: Switch implementation to using bitmap
From: Nikolay Borisov <hidden>
Date: 2025-07-28 11:15:34
Also in:
lkml
Subsystem:
lockdown security module, security subsystem, the rest · Maintainers:
Nicolas Bouchinet, Xiu Jianfeng, Paul Moore, James Morris, "Serge E. Hallyn", Linus Torvalds
Tracking the lockdown at the depth granularity rather than at the individual is somewhat inflexible as it provides an "all or nothing" approach. Instead there are use cases where it will be useful to be able to lockdown individual features - TDX for example wants to disable access to just /dev/mem. To accommodate this use case switch the internal implementation to using a bitmap so that individual lockdown features can be turned on. At the same time retain the existing semantic where INTEGRITY_MAX/CONFIDENTIALITY_MAX are treated as wildcards meaning "lock everything below me". Signed-off-by: Nikolay Borisov <redacted> --- security/lockdown/lockdown.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c
index cf83afa1d879..5014d18c423f 100644
--- a/security/lockdown/lockdown.c
+++ b/security/lockdown/lockdown.c@@ -10,12 +10,13 @@ * 2 of the Licence, or (at your option) any later version. */ +#include <linux/bitmap.h> #include <linux/security.h> #include <linux/export.h> #include <linux/lsm_hooks.h> #include <uapi/linux/lsm.h> -static enum lockdown_reason kernel_locked_down; +static DECLARE_BITMAP(kernel_locked_down, LOCKDOWN_CONFIDENTIALITY_MAX); static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, LOCKDOWN_INTEGRITY_MAX,
@@ -26,10 +27,15 @@ static const enum lockdown_reason lockdown_levels[] = {LOCKDOWN_NONE, */ static int lock_kernel_down(const char *where, enum lockdown_reason level) { - if (kernel_locked_down >= level) - return -EPERM; - kernel_locked_down = level; + if (level > LOCKDOWN_CONFIDENTIALITY_MAX) + return -EINVAL; + + if (level == LOCKDOWN_INTEGRITY_MAX || level == LOCKDOWN_CONFIDENTIALITY_MAX) + bitmap_set(kernel_locked_down, 1, level); + else + bitmap_set(kernel_locked_down, level, 1); + pr_notice("Kernel is locked down from %s; see man kernel_lockdown.7\n", where); return 0;
@@ -62,13 +68,12 @@ static int lockdown_is_locked_down(enum lockdown_reason what) "Invalid lockdown reason")) return -EPERM; - if (kernel_locked_down >= what) { + if (test_bit(what, kernel_locked_down)) { if (lockdown_reasons[what]) pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n", current->comm, lockdown_reasons[what]); return -EPERM; } - return 0; }
@@ -105,7 +110,7 @@ static ssize_t lockdown_read(struct file *filp, char __user *buf, size_t count, if (lockdown_reasons[level]) { const char *label = lockdown_reasons[level]; - if (kernel_locked_down == level) + if (test_bit(level, kernel_locked_down)) offset += sprintf(temp+offset, "[%s] ", label); else offset += sprintf(temp+offset, "%s ", label);
--
2.34.1