Re: [PATCH] parisc: sigaltstack doesn't round ss.ss_sp as required

[Rolf Eike Beer <eike-kernel@sf-tec.de>]

[-- Attachment #1: Type: text/plain, Size: 1268 bytes --]

John David Anglin wrote:
> On 24-Nov-12, at 10:05 AM, John David Anglin wrote:
> > In trying to build the debian libsigsegv2 package, I found that
> > sigaltstack
> > doesn't round ss.ss_sp.  The tests intentionally pass an unaligned
> > pointer.
> > This results in the two stack overflow tests failing.
> 
> The attached patch fixes this issue.

diff --git a/arch/parisc/kernel/signal.c b/arch/parisc/kernel/signal.c
index 594459b..324644d 100644
--- a/arch/parisc/kernel/signal.c
+++ b/arch/parisc/kernel/signal.c
@@ -188,8 +188,10 @@ get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
 	DBG(1,"get_sigframe: ka = %#lx, sp = %#lx, frame_size = %#lx\n",
 			(unsigned long)ka, sp, frame_size);
 	
+	/* Align alternate stack and reserve 64 bytes for the signal
+	   handler's frame marker.  */
 	if ((ka->sa.sa_flags & SA_ONSTACK) != 0 && ! sas_ss_flags(sp))
-		sp = current->sas_ss_sp; /* Stacks grow up! */
+		sp = (current->sas_ss_sp + 0x7f) & ~0x3f; /* Stacks grow up! */
 
 	DBG(1,"get_sigframe: Returning sp = %#lx\n", (unsigned long)sp);
 	return (void __user *) sp; /* Stacks grow up.  Fun. */

What about something like this (entirely untested, but you'll get the idea):

sp = round_down(current->sas_ss_sp + 64, 64);

Greetings.

Eike

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 198 bytes --]