Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6:
  sparc: Fix SA_ONSTACK signal handling.

1 files changed, 17 insertions, 4 deletions

diff --git a/arch/sparc64/kernel/signal.c b/arch/sparc64/kernel/signal.c
index 45d6bf6..07c0443 100644
--- a/arch/sparc64/kernel/signal.c
+++ b/arch/sparc64/kernel/signal.c
@@ -376,16 +376,29 @@ save_fpu_state(struct pt_regs *regs, __siginfo_fpu_t __user *fpu)
 
 static inline void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, unsigned long framesize)
 {
-	unsigned long sp;
+	unsigned long sp = regs->u_regs[UREG_FP] + STACK_BIAS;
 
-	sp = regs->u_regs[UREG_FP] + STACK_BIAS;
+	/*
+	 * If we are on the alternate signal stack and would overflow it, don't.
+	 * Return an always-bogus address instead so we will die with SIGSEGV.
+	 */
+	if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize)))
+		return (void __user *) -1L;
 
 	/* This is the X/Open sanctioned signal stack switching.  */
 	if (ka->sa.sa_flags & SA_ONSTACK) {
-		if (!on_sig_stack(sp) &&
-		    !((current->sas_ss_sp + current->sas_ss_size) & 7))
+		if (sas_ss_flags(sp) == 0)
 			sp = current->sas_ss_sp + current->sas_ss_size;
 	}
+
+	/* Always align the stack frame.  This handles two cases.  First,
+	 * sigaltstack need not be mindful of platform specific stack
+	 * alignment.  Second, if we took this signal because the stack
+	 * is not aligned properly, we'd like to take the signal cleanly
+	 * and report that.
+	 */
+	sp &= ~7UL;
+
 	return (void __user *)(sp - framesize);
 }