path: root/security/security.c
diff options
authorLinus Torvalds <torvalds@linux-foundation.org>2019-09-28 08:14:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-09-28 08:14:15 -0700
commitaefcf2f4b58155d27340ba5f9ddbe9513da8286d (patch)
treea8ae994ca71b2e43e3075c796165e5ed62e28e42 /security/security.c
parentMerge branch 'next-integrity' of git://git.kernel.org/pub/scm/linux/kernel/git/zohar/linux-integrity (diff)
parentkexec: Fix file verification on S390 (diff)
Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull kernel lockdown mode from James Morris: "This is the latest iteration of the kernel lockdown patchset, from Matthew Garrett, David Howells and others. From the original description: This patchset introduces an optional kernel lockdown feature, intended to strengthen the boundary between UID 0 and the kernel. When enabled, various pieces of kernel functionality are restricted. Applications that rely on low-level access to either hardware or the kernel may cease working as a result - therefore this should not be enabled without appropriate evaluation beforehand. The majority of mainstream distributions have been carrying variants of this patchset for many years now, so there's value in providing a doesn't meet every distribution requirement, but gets us much closer to not requiring external patches. There are two major changes since this was last proposed for mainline: - Separating lockdown from EFI secure boot. Background discussion is covered here: https://lwn.net/Articles/751061/ - Implementation as an LSM, with a default stackable lockdown LSM module. This allows the lockdown feature to be policy-driven, rather than encoding an implicit policy within the mechanism. The new locked_down LSM hook is provided to allow LSMs to make a policy decision around whether kernel functionality that would allow tampering with or examining the runtime state of the kernel should be permitted. The included lockdown LSM provides an implementation with a simple policy intended for general purpose use. This policy provides a coarse level of granularity, controllable via the kernel command line: lockdown={integrity|confidentiality} Enable the kernel lockdown feature. If set to integrity, kernel features that allow userland to modify the running kernel are disabled. If set to confidentiality, kernel features that allow userland to extract confidential information from the kernel are also disabled. This may also be controlled via /sys/kernel/security/lockdown and overriden by kernel configuration. New or existing LSMs may implement finer-grained controls of the lockdown features. Refer to the lockdown_reason documentation in include/linux/security.h for details. The lockdown feature has had signficant design feedback and review across many subsystems. This code has been in linux-next for some weeks, with a few fixes applied along the way. Stephen Rothwell noted that commit 9d1f8be5cf42 ("bpf: Restrict bpf when kernel lockdown is in confidentiality mode") is missing a Signed-off-by from its author. Matthew responded that he is providing this under category (c) of the DCO" * 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (31 commits) kexec: Fix file verification on S390 security: constify some arrays in lockdown LSM lockdown: Print current->comm in restriction messages efi: Restrict efivar_ssdt_load when the kernel is locked down tracefs: Restrict tracefs when the kernel is locked down debugfs: Restrict debugfs when the kernel is locked down kexec: Allow kexec_file() with appropriate IMA policy when locked down lockdown: Lock down perf when in confidentiality mode bpf: Restrict bpf when kernel lockdown is in confidentiality mode lockdown: Lock down tracing and perf kprobes when in confidentiality mode lockdown: Lock down /proc/kcore x86/mmiotrace: Lock down the testmmiotrace module lockdown: Lock down module params that specify hardware parameters (eg. ioport) lockdown: Lock down TIOCSSERIAL lockdown: Prohibit PCMCIA CIS storage when the kernel is locked down acpi: Disable ACPI table override if the kernel is locked down acpi: Ignore acpi_rsdp kernel param when the kernel has been locked down ACPI: Limit access to custom_method when the kernel is locked down x86/msr: Restrict MSR access when the kernel is locked down x86: Lock down IO port access when the kernel is locked down ...
Diffstat (limited to 'security/security.c')
1 files changed, 48 insertions, 8 deletions
diff --git a/security/security.c b/security/security.c
index 25ee5c75551f..1bc000f834e2 100644
--- a/security/security.c
+++ b/security/security.c
@@ -33,6 +33,7 @@
/* How many LSMs were built into the kernel? */
#define LSM_COUNT (__end_lsm_info - __start_lsm_info)
+#define EARLY_LSM_COUNT (__end_early_lsm_info - __start_early_lsm_info)
struct security_hook_heads security_hook_heads __lsm_ro_after_init;
static BLOCKING_NOTIFIER_HEAD(blocking_lsm_notifier_chain);
@@ -277,6 +278,8 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
static void __init lsm_early_cred(struct cred *cred);
static void __init lsm_early_task(struct task_struct *task);
+static int lsm_append(const char *new, char **result);
static void __init ordered_lsm_init(void)
struct lsm_info **lsm;
@@ -323,6 +326,26 @@ static void __init ordered_lsm_init(void)
+int __init early_security_init(void)
+ int i;
+ struct hlist_head *list = (struct hlist_head *) &security_hook_heads;
+ struct lsm_info *lsm;
+ for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct hlist_head);
+ i++)
+ INIT_HLIST_HEAD(&list[i]);
+ for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
+ if (!lsm->enabled)
+ lsm->enabled = &lsm_enabled_true;
+ prepare_lsm(lsm);
+ initialize_lsm(lsm);
+ }
+ return 0;
* security_init - initializes the security framework
@@ -330,14 +353,18 @@ static void __init ordered_lsm_init(void)
int __init security_init(void)
- int i;
- struct hlist_head *list = (struct hlist_head *) &security_hook_heads;
+ struct lsm_info *lsm;
pr_info("Security Framework initializing\n");
- for (i = 0; i < sizeof(security_hook_heads) / sizeof(struct hlist_head);
- i++)
- INIT_HLIST_HEAD(&list[i]);
+ /*
+ * Append the names of the early LSM modules now that kmalloc() is
+ * available
+ */
+ for (lsm = __start_early_lsm_info; lsm < __end_early_lsm_info; lsm++) {
+ if (lsm->enabled)
+ lsm_append(lsm->name, &lsm_names);
+ }
/* Load LSMs in specified order. */
@@ -384,7 +411,7 @@ static bool match_last_lsm(const char *list, const char *lsm)
return !strcmp(last, lsm);
-static int lsm_append(char *new, char **result)
+static int lsm_append(const char *new, char **result)
char *cp;
@@ -422,8 +449,15 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
hooks[i].lsm = lsm;
hlist_add_tail_rcu(&hooks[i].list, hooks[i].head);
- if (lsm_append(lsm, &lsm_names) < 0)
- panic("%s - Cannot get early memory.\n", __func__);
+ /*
+ * Don't try to append during early_security_init(), we'll come back
+ * and fix this up afterwards.
+ */
+ if (slab_is_available()) {
+ if (lsm_append(lsm, &lsm_names) < 0)
+ panic("%s - Cannot get early memory.\n", __func__);
+ }
int call_blocking_lsm_notifier(enum lsm_event event, void *data)
@@ -2364,3 +2398,9 @@ void security_bpf_prog_free(struct bpf_prog_aux *aux)
call_void_hook(bpf_prog_free_security, aux);
+int security_locked_down(enum lockdown_reason what)
+ return call_int_hook(locked_down, 0, what);