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    SubjectRe: [PATCH v3 1/2] security: add fault injection capability
    On Thu, Oct 29, 2020 at 7:35 PM Aleksandr Nogikh
    <aleksandrnogikh@gmail.com> 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>

    Reviewed-by: Andrey Konovalov <andreyknvl@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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