[S390] Protect against sigaltstack wraparound.

This is just a port of 83bd01024b
"x86: protect against sigaltstack wraparound".

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

arch/s390/kernel/compat_signal.c

@@ -428,6 +428,10 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 	/* Default to using normal stack */
 	sp = (unsigned long) A(regs->gprs[15]);
 
+	/* Overflow on alternate signal stack gives SIGSEGV. */
+	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
+		return (void __user *) -1UL;
+
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
 		if (! sas_ss_flags(sp))
@@ -461,6 +465,9 @@ static int setup_frame32(int sig, struct k_sigaction *ka,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe32)))
 		goto give_sigsegv;
 
+	if (frame == (void __user *) -1UL)
+		goto give_sigsegv;
+
 	if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE32))
 		goto give_sigsegv;
 
@@ -514,6 +521,9 @@ static int setup_rt_frame32(int sig, struct k_sigaction *ka, siginfo_t *info,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe32)))
 		goto give_sigsegv;
 
+	if (frame == (void __user *) -1UL)
+		goto give_sigsegv;
+
 	if (copy_siginfo_to_user32(&frame->info, info))
 		goto give_sigsegv;
 

arch/s390/kernel/signal.c

@@ -235,6 +235,10 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
 	/* Default to using normal stack */
 	sp = regs->gprs[15];
 
+	/* Overflow on alternate signal stack gives SIGSEGV. */
+	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
+		return (void __user *) -1UL;
+
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
 		if (! sas_ss_flags(sp))
@@ -270,6 +274,9 @@ static int setup_frame(int sig, struct k_sigaction *ka,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe)))
 		goto give_sigsegv;
 
+	if (frame == (void __user *) -1UL)
+		goto give_sigsegv;
+
 	if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE))
 		goto give_sigsegv;
 
@@ -327,6 +334,9 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
 	if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe)))
 		goto give_sigsegv;
 
+	if (frame == (void __user *) -1UL)
+		goto give_sigsegv;
+
 	if (copy_siginfo_to_user(&frame->info, info))
 		goto give_sigsegv;