diff mbox series

[RFC,1/1] security: add fault injection capability

Message ID 20201015104649.2104432-2-a.nogikh@gmail.com
State New
Headers show
Series security: add fault injection to LSM hooks | expand

Commit Message

Aleksandr Nogikh Oct. 15, 2020, 10:46 a.m. UTC
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>
---
 lib/Kconfig.debug   |  6 +++++
 security/security.c | 53 ++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 56 insertions(+), 3 deletions(-)

Comments

Serge E. Hallyn Oct. 15, 2020, 3:30 p.m. UTC | #1
On Thu, Oct 15, 2020 at 10:46:49AM +0000, Aleksandr Nogikh wrote:
> 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>
> ---
>  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 08c82666cf3e..0c9913ebe1c1 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..bd4dbe720098 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 should_fail_lsm_hook(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 should_fail_lsm_hook(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 = should_fail_lsm_hook();			\

seeing 'should_fail' here, kind of out of context, would be confusing to
thousands of ppl reading the code and wondering why it should fail.  maybe
"inject_fail_lsm_hook()" ?

> +	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;							\
>  })
>  
> -- 
> 2.28.0.1011.ga647a8990f-goog
Aleksandr Nogikh Oct. 16, 2020, 7 a.m. UTC | #2
On Thu, 15 Oct 2020 at 18:30, Serge E. Hallyn <serge@hallyn.com> wrote:
[...]
> seeing 'should_fail' here, kind of out of context, would be confusing to
> thousands of ppl reading the code and wondering why it should fail.  maybe
> "inject_fail_lsm_hook()" ?

Sounds reasonable, thank you for the suggestion. I'll rename this
function in v2.
diff mbox series

Patch

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 08c82666cf3e..0c9913ebe1c1 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..bd4dbe720098 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 should_fail_lsm_hook(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 should_fail_lsm_hook(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 = should_fail_lsm_hook();			\
+	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;							\
 })