1 files changed, 17 insertions, 4 deletions

diff --git a/arch/sparc64/kernel/signal.c b/arch/sparc64/kernel/signal.c
index 45d6bf632daa..07c0443ea3f5 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);
 }