signal: Don't always set SA_IMMUTABLE for forced signals

[linux-2.6-block.git] / kernel / signal.c

diff --git a/kernel/signal.c b/kernel/signal.c
index 6f3476dc787325c136a8a79e58e9963b1b57bc67..7815e1bbeddc570fb885e995e4e61668aa422069 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1298,6 +1298,12 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
        return ret;
 }
 
+enum sig_handler {
+       HANDLER_CURRENT, /* If reachable use the current handler */
+       HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */
+       HANDLER_EXIT,    /* Only visible as the process exit code */
+};
+
 /*
  * Force a signal that the process can't ignore: if necessary
  * we unblock the signal and change any SIG_IGN to SIG_DFL.
@@ -1310,7 +1316,8 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p
  * that is why we also clear SIGNAL_UNKILLABLE.
  */
 static int
-force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool sigdfl)
+force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t,
+       enum sig_handler handler)
 {
        unsigned long int flags;
        int ret, blocked, ignored;
@@ -1321,8 +1328,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
        action = &t->sighand->action[sig-1];
        ignored = action->sa.sa_handler == SIG_IGN;
        blocked = sigismember(&t->blocked, sig);
-       if (blocked || ignored || sigdfl) {
+       if (blocked || ignored || (handler != HANDLER_CURRENT)) {
                action->sa.sa_handler = SIG_DFL;
+               if (handler == HANDLER_EXIT)
+                       action->sa.sa_flags |= SA_IMMUTABLE;
                if (blocked) {
                        sigdelset(&t->blocked, sig);
                        recalc_sigpending_and_wake(t);
@@ -1342,7 +1351,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool
 
 int force_sig_info(struct kernel_siginfo *info)
 {
-       return force_sig_info_to_task(info, current, false);
+       return force_sig_info_to_task(info, current, HANDLER_CURRENT);
 }
 
 /*
@@ -1649,6 +1658,19 @@ void force_sig(int sig)
 }
 EXPORT_SYMBOL(force_sig);
 
+void force_fatal_sig(int sig)
+{
+       struct kernel_siginfo info;
+
+       clear_siginfo(&info);
+       info.si_signo = sig;
+       info.si_errno = 0;
+       info.si_code = SI_KERNEL;
+       info.si_pid = 0;
+       info.si_uid = 0;
+       force_sig_info_to_task(&info, current, HANDLER_SIG_DFL);
+}
+
 /*
  * When things go south during signal handling, we
  * will force a SIGSEGV. And if the signal that caused
@@ -1657,15 +1679,10 @@ EXPORT_SYMBOL(force_sig);
  */
 void force_sigsegv(int sig)
 {
-       struct task_struct *p = current;
-
-       if (sig == SIGSEGV) {
-               unsigned long flags;
-               spin_lock_irqsave(&p->sighand->siglock, flags);
-               p->sighand->action[sig - 1].sa.sa_handler = SIG_DFL;
-               spin_unlock_irqrestore(&p->sighand->siglock, flags);
-       }
-       force_sig(SIGSEGV);
+       if (sig == SIGSEGV)
+               force_fatal_sig(SIGSEGV);
+       else
+               force_sig(SIGSEGV);
 }
 
 int force_sig_fault_to_task(int sig, int code, void __user *addr
@@ -1684,7 +1701,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr
        info.si_flags = flags;
        info.si_isr = isr;
 #endif
-       return force_sig_info_to_task(&info, t, false);
+       return force_sig_info_to_task(&info, t, HANDLER_CURRENT);
 }
 
 int force_sig_fault(int sig, int code, void __user *addr
@@ -1804,7 +1821,8 @@ int force_sig_seccomp(int syscall, int reason, bool force_coredump)
        info.si_errno = reason;
        info.si_arch = syscall_get_arch(current);
        info.si_syscall = syscall;
-       return force_sig_info_to_task(&info, current, force_coredump);
+       return force_sig_info_to_task(&info, current,
+               force_coredump ? HANDLER_EXIT : HANDLER_CURRENT);
 }
 
 /* For the crazy architectures that include trap information in
@@ -2704,7 +2722,8 @@ relock:
                if (!signr)
                        break; /* will return 0 */
 
-               if (unlikely(current->ptrace) && signr != SIGKILL) {
+               if (unlikely(current->ptrace) && (signr != SIGKILL) &&
+                   !(sighand->action[signr -1].sa.sa_flags & SA_IMMUTABLE)) {
                        signr = ptrace_signal(signr, &ksig->info);
                        if (!signr)
                                continue;
@@ -4054,6 +4073,10 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
        k = &p->sighand->action[sig-1];
 
        spin_lock_irq(&p->sighand->siglock);
+       if (k->sa.sa_flags & SA_IMMUTABLE) {
+               spin_unlock_irq(&p->sighand->siglock);
+               return -EINVAL;
+       }
        if (oact)
                *oact = *k;