linux-kernel - [ 22/37] sparc64: not any error from do_sigaltstack() should fail rt

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Message-Id: <20121130183859.634524718@linuxfoundation.org>
Date:	Fri, 30 Nov 2012 10:46:09 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Al Viro <viro@...iv.linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 22/37] sparc64: not any error from do_sigaltstack() should fail rt_sigreturn()

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Al Viro <viro@...iv.linux.org.uk>

commit fae2ae2a900a5c7bb385fe4075f343e7e2d5daa2 upstream.

If a signal handler is executed on altstack and another signal comes,
we will end up with rt_sigreturn() on return from the second handler
getting -EPERM from do_sigaltstack().  It's perfectly OK, since we
are not asking to change the settings; in fact, they couldn't have been
changed during the second handler execution exactly because we'd been
on altstack all along.  64bit sigreturn on sparc treats any error from
do_sigaltstack() as "SIGSEGV now"; we need to switch to the same semantics
we are using on other architectures.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/sparc/kernel/signal_64.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/arch/sparc/kernel/signal_64.c
+++ b/arch/sparc/kernel/signal_64.c
@@ -309,9 +309,7 @@ void do_rt_sigreturn(struct pt_regs *reg
 		err |= restore_fpu_state(regs, fpu_save);

 	err |= __copy_from_user(&set, &sf->mask, sizeof(sigset_t));
-	err |= do_sigaltstack(&sf->stack, NULL, (unsigned long)sf);
-
-	if (err)
+	if (err || do_sigaltstack(&sf->stack, NULL, (unsigned long)sf) == -EFAULT)
 		goto segv;

 	err |= __get_user(rwin_save, &sf->rwin_save);

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