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Subject[PATCH v3 1/2] security: add fault injection capability
Date
From: Aleksandr Nogikh <nogikh@google.com>

Add a fault injection capability to call_int_hook macro. This will
facilitate testing of fault tolerance of the code that invokes
security hooks as well as the fault tolerance of the LSM
implementations themselves.

Add a KConfig option (CONFIG_FAIL_LSM_HOOKS) that controls whether the
capability is enabled. In order to enable configuration from the user
space, add the standard debugfs entries for fault injection (if
CONFIG_FAULT_INJECTION_DEBUG_FS is enabled).

Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
---
v2:
* Renamed should_fail_lsm_hook() to lsm_hooks_inject_fail().
---
lib/Kconfig.debug | 6 +++++
security/security.c | 53 ++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 56 insertions(+), 3 deletions(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 537cf3c2937d..80d289591e29 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1803,6 +1803,12 @@ config FAIL_MAKE_REQUEST
help
Provide fault-injection capability for disk IO.

+config FAIL_LSM_HOOKS
+ bool "Fault-injection capability for LSM hooks"
+ depends on FAULT_INJECTION
+ help
+ Provide fault-injection capability for LSM hooks.
+
config FAIL_IO_TIMEOUT
bool "Fault-injection capability for faking disk interrupts"
depends on FAULT_INJECTION && BLOCK
diff --git a/security/security.c b/security/security.c
index 69ff6e2e2cd4..1105ad0f6891 100644
--- a/security/security.c
+++ b/security/security.c
@@ -28,6 +28,7 @@
#include <linux/backing-dev.h>
#include <linux/string.h>
#include <linux/msg.h>
+#include <linux/fault-inject.h>
#include <net/flow.h>

#define MAX_LSM_EVM_XATTR 2
@@ -669,6 +670,51 @@ static void __init lsm_early_task(struct task_struct *task)
panic("%s: Early task alloc failed.\n", __func__);
}

+
+#ifdef CONFIG_FAIL_LSM_HOOKS
+
+static struct {
+ struct fault_attr attr;
+ int retval;
+} fail_lsm_hooks = {
+ .attr = FAULT_ATTR_INITIALIZER,
+ .retval = -EACCES
+};
+
+static int __init setup_fail_lsm_hooks(char *str)
+{
+ return setup_fault_attr(&fail_lsm_hooks.attr, str);
+}
+__setup("fail_lsm_hooks=", setup_fail_lsm_hooks);
+
+static int lsm_hooks_inject_fail(void)
+{
+ return should_fail(&fail_lsm_hooks.attr, 1) ? fail_lsm_hooks.retval : 0;
+}
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int __init fail_lsm_hooks_debugfs(void)
+{
+ umode_t mode = S_IFREG | 0600;
+ struct dentry *dir;
+
+ dir = fault_create_debugfs_attr("fail_lsm_hooks", NULL,
+ &fail_lsm_hooks.attr);
+ debugfs_create_u32("retval", mode, dir, &fail_lsm_hooks.retval);
+ return 0;
+}
+
+late_initcall(fail_lsm_hooks_debugfs);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#else
+
+static inline int lsm_hooks_inject_fail(void) { return 0; }
+
+#endif /* CONFIG_FAIL_LSM_HOOKS */
+
/*
* The default value of the LSM hook is defined in linux/lsm_hook_defs.h and
* can be accessed with:
@@ -707,16 +753,17 @@ static void __init lsm_early_task(struct task_struct *task)
} while (0)

#define call_int_hook(FUNC, IRC, ...) ({ \
- int RC = IRC; \
- do { \
+ int RC = lsm_hooks_inject_fail(); \
+ if (RC == 0) { \
struct security_hook_list *P; \
+ RC = IRC; \
\
hlist_for_each_entry(P, &security_hook_heads.FUNC, list) { \
RC = P->hook.FUNC(__VA_ARGS__); \
if (RC != 0) \
break; \
} \
- } while (0); \
+ } \
RC; \
})

--
2.29.1.341.ge80a0c044ae-goog
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