diff options
| -rw-r--r-- | kernel/seccomp.c | 10 | ||||
| -rw-r--r-- | kernel/signal.c | 5 | ||||
| -rw-r--r-- | samples/seccomp/dropper.c | 9 |
3 files changed, 20 insertions, 4 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 4d8f44a17727..db10e73d06e0 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -29,6 +29,9 @@ #include <linux/syscalls.h> #include <linux/sysctl.h> +/* Not exposed in headers: strictly internal use only. */ +#define SECCOMP_MODE_DEAD (SECCOMP_MODE_FILTER + 1) + #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER #include <asm/syscall.h> #endif @@ -1010,6 +1013,7 @@ static void __secure_computing_strict(int this_syscall) #ifdef SECCOMP_DEBUG dump_stack(); #endif + current->seccomp.mode = SECCOMP_MODE_DEAD; seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); do_exit(SIGKILL); } @@ -1261,6 +1265,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, case SECCOMP_RET_KILL_THREAD: case SECCOMP_RET_KILL_PROCESS: default: + current->seccomp.mode = SECCOMP_MODE_DEAD; seccomp_log(this_syscall, SIGSYS, action, true); /* Dump core only if this is the last remaining thread. */ if (action != SECCOMP_RET_KILL_THREAD || @@ -1309,6 +1314,11 @@ int __secure_computing(const struct seccomp_data *sd) return 0; case SECCOMP_MODE_FILTER: return __seccomp_filter(this_syscall, sd, false); + /* Surviving SECCOMP_RET_KILL_* must be proactively impossible. */ + case SECCOMP_MODE_DEAD: + WARN_ON_ONCE(1); + do_exit(SIGKILL); + return -1; default: BUG(); } diff --git a/kernel/signal.c b/kernel/signal.c index 38602738866e..9b04631acde8 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1342,9 +1342,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, } /* * Don't clear SIGNAL_UNKILLABLE for traced tasks, users won't expect - * debugging to leave init killable. + * debugging to leave init killable. But HANDLER_EXIT is always fatal. */ - if (action->sa.sa_handler == SIG_DFL && !t->ptrace) + if (action->sa.sa_handler == SIG_DFL && + (!t->ptrace || (handler == HANDLER_EXIT))) t->signal->flags &= ~SIGNAL_UNKILLABLE; ret = send_signal(sig, info, t, PIDTYPE_PID); spin_unlock_irqrestore(&t->sighand->siglock, flags); diff --git a/samples/seccomp/dropper.c b/samples/seccomp/dropper.c index cc0648eb389e..4bca4b70f665 100644 --- a/samples/seccomp/dropper.c +++ b/samples/seccomp/dropper.c @@ -25,7 +25,7 @@ #include <sys/prctl.h> #include <unistd.h> -static int install_filter(int nr, int arch, int error) +static int install_filter(int arch, int nr, int error) { struct sock_filter filter[] = { BPF_STMT(BPF_LD+BPF_W+BPF_ABS, @@ -42,6 +42,10 @@ static int install_filter(int nr, int arch, int error) .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])), .filter = filter, }; + if (error == -1) { + struct sock_filter kill = BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL); + filter[4] = kill; + } if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { perror("prctl(NO_NEW_PRIVS)"); return 1; @@ -57,9 +61,10 @@ int main(int argc, char **argv) { if (argc < 5) { fprintf(stderr, "Usage:\n" - "dropper <syscall_nr> <arch> <errno> <prog> [<args>]\n" + "dropper <arch> <syscall_nr> <errno> <prog> [<args>]\n" "Hint: AUDIT_ARCH_I386: 0x%X\n" " AUDIT_ARCH_X86_64: 0x%X\n" + " errno == -1 means SECCOMP_RET_KILL\n" "\n", AUDIT_ARCH_I386, AUDIT_ARCH_X86_64); return 1; } |