Re: [PATCH v4 2/4] seccomp: Add sysctl to configure actions that should be logged

On 02/15/2017 07:10 PM, Kees Cook wrote: > On Mon, Feb 13, 2017 at 7:55 PM, Tyler Hicks <tyhicks(a)canonical.com&gt; wrote: >> diff --git a/kernel/seccomp.c b/kernel/seccomp.c >> index e36dfe9..270a227 100644 >> --- a/kernel/seccomp.c >> +++ b/kernel/seccomp.c >> @@ -509,6 +509,22 @@ static void seccomp_send_sigsys(int syscall, int reason) >> } >> #endif /* CONFIG_SECCOMP_FILTER */ >> >> +static u32 seccomp_log_max_action = SECCOMP_RET_KILL; >> + >> +static inline void seccomp_log(unsigned long syscall, long signr, u32 action) >> +{ >> + /* Force an audit message to be emitted when the action is not greater >> + * than the configured maximum action. >> + */ >> + if (action <= seccomp_log_max_action) >> + return __audit_seccomp(syscall, signr, action); >> + >> + /* Let the audit subsystem decide if the action should be audited based >> + * on whether the current task itself is being audited. >> + */ > > Nitpick on comment style, please use: > > /* > * line 1 > * line 2... > */ No problem. > >> + return audit_seccomp(syscall, signr, action); >> +} >> + >> /* >> * Secure computing mode 1 allows only read/write/exit/sigreturn. >> * To be fully secure this must be combined with rlimit >> @@ -534,7 +550,7 @@ static void __secure_computing_strict(int this_syscall) >> #ifdef SECCOMP_DEBUG >> dump_stack(); >> #endif >> - audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL); >> + seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL); >> do_exit(SIGKILL); >> } >> >> @@ -633,18 +649,30 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, >> return 0; >> >> case SECCOMP_RET_ALLOW: >> + /* Open-coded seccomp_log(), optimized for the RET_ALLOW hot >> + * path. >> + * >> + * We only want to log RET_ALLOW actions when the admin has >> + * configured them to be logged via the log_max_action sysctl. >> + * Therefore, call __audit_seccomp() directly so that RET_ALLOW >> + * actions are not audited simply because the task is being >> + * audited. >> + */ >> + if (unlikely(seccomp_log_max_action == SECCOMP_RET_ALLOW)) >> + __audit_seccomp(this_syscall, 0, action); >> + >> return 0; >> >> case SECCOMP_RET_KILL: >> default: >> - audit_seccomp(this_syscall, SIGSYS, action); >> + seccomp_log(this_syscall, SIGSYS, action); >> do_exit(SIGSYS); >> } >> >> unreachable(); >> >> skip: >> - audit_seccomp(this_syscall, 0, action); >> + seccomp_log(this_syscall, 0, action); >> return -1; >> } >> #else >> @@ -917,12 +945,96 @@ long seccomp_get_filter(struct task_struct *task, unsigned long filter_off, >> #define SECCOMP_RET_TRACE_NAME "trace" >> #define SECCOMP_RET_ALLOW_NAME "allow" >> >> +/* Largest strlen() of all action names */ >> +#define SECCOMP_RET_MAX_NAME_LEN 5 >> + >> static char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " " >> SECCOMP_RET_TRAP_NAME " " >> SECCOMP_RET_ERRNO_NAME " " >> SECCOMP_RET_TRACE_NAME " " >> SECCOMP_RET_ALLOW_NAME; >> >> +struct seccomp_action_name { >> + u32 action; >> + const char *name; >> +}; >> + >> +static struct seccomp_action_name seccomp_action_names[] = { > > As long as I'm nit-picking, this can be const too. :) I'll have to cast to a non-const pointer when assigning ctl_table.data but I think that's fine in this case.