linux-kernel - [PATCH 3.16 047/306] arc: don't leak bits of kernel stack into coredump

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Date:   Wed, 15 Feb 2017 22:41:40 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Al Viro" <viro@...iv.linux.org.uk>
Subject: [PATCH 3.16 047/306] arc: don't leak bits of kernel stack into
 coredump

3.16.40-rc1 review patch.  If anyone has any objections, please let me know.

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

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

commit 7798bf2140ebcc36eafec6a4194fffd8d585d471 upstream.

On faulting sigreturn we do get SIGSEGV, all right, but anything
we'd put into pt_regs could end up in the coredump.  And since
__copy_from_user() never zeroed on arc, we'd better bugger off
on its failure without copying random uninitialized bits of
kernel stack into pt_regs...

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
[bwh: Backported to 3.16:
 - Adjust context
 - Don't change the single return statement]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arc/kernel/signal.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/arch/arc/kernel/signal.c
+++ b/arch/arc/kernel/signal.c
@@ -80,11 +80,12 @@ static int restore_usr_regs(struct pt_re
 	int err;
 
 	err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
-	if (!err)
-		set_current_blocked(&set);
-
 	err |= __copy_from_user(regs, &(sf->uc.uc_mcontext.regs.scratch),
 				sizeof(sf->uc.uc_mcontext.regs.scratch));
+	if (err)
+		return err;
+
+	set_current_blocked(&set);
 
 	return err;
 }