On Thu, 29 Oct 2020 at 19:35, Aleksandr Nogikh
<aleksandrnog...@gmail.com> wrote:
> From: Aleksandr Nogikh <nog...@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 <nog...@google.com>
Reviewed-by: Marco Elver <el...@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
>
