From f5e7d8bdb51ec52b3530c85f42bb7aff8a495330 Mon Sep 17 00:00:00 2001
From: Eric van Gyzen <vangyzen@FreeBSD.org>
Date: Mon, 26 Nov 2018 20:50:55 +0000
Subject: [PATCH] Prevent kernel stack disclosure in getcontext/swapcontext

Expand r338982 to cover freebsd32 interfaces on amd64, mips, and powerpc.

MFC after:	2 days
Security:	FreeBSD-EN-18:12.mem
Security:	CVE-2018-17155
Sponsored by:	Dell EMC Isilon
---
 sys/amd64/ia32/ia32_signal.c       | 2 ++
 sys/mips/mips/freebsd32_machdep.c  | 2 ++
 sys/powerpc/powerpc/exec_machdep.c | 2 ++
 3 files changed, 6 insertions(+)

diff --git a/sys/amd64/ia32/ia32_signal.c b/sys/amd64/ia32/ia32_signal.c
index f0ed9bd3eb0c..72f35af75b85 100644
--- a/sys/amd64/ia32/ia32_signal.c
+++ b/sys/amd64/ia32/ia32_signal.c
@@ -261,6 +261,7 @@ freebsd32_getcontext(struct thread *td, struct freebsd32_getcontext_args *uap)
 	if (uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		ia32_get_mcontext(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;
@@ -301,6 +302,7 @@ freebsd32_swapcontext(struct thread *td, struct freebsd32_swapcontext_args *uap)
 	if (uap->oucp == NULL || uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		ia32_get_mcontext(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;
diff --git a/sys/mips/mips/freebsd32_machdep.c b/sys/mips/mips/freebsd32_machdep.c
index 73c5848029fa..0c32cb65fbef 100644
--- a/sys/mips/mips/freebsd32_machdep.c
+++ b/sys/mips/mips/freebsd32_machdep.c
@@ -294,6 +294,7 @@ freebsd32_getcontext(struct thread *td, struct freebsd32_getcontext_args *uap)
 	if (uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		get_mcontext32(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;
@@ -333,6 +334,7 @@ freebsd32_swapcontext(struct thread *td, struct freebsd32_swapcontext_args *uap)
 	if (uap->oucp == NULL || uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		get_mcontext32(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;
diff --git a/sys/powerpc/powerpc/exec_machdep.c b/sys/powerpc/powerpc/exec_machdep.c
index 718962ffcb6f..583735099347 100644
--- a/sys/powerpc/powerpc/exec_machdep.c
+++ b/sys/powerpc/powerpc/exec_machdep.c
@@ -785,6 +785,7 @@ freebsd32_getcontext(struct thread *td, struct freebsd32_getcontext_args *uap)
 	if (uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		get_mcontext32(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;
@@ -824,6 +825,7 @@ freebsd32_swapcontext(struct thread *td, struct freebsd32_swapcontext_args *uap)
 	if (uap->oucp == NULL || uap->ucp == NULL)
 		ret = EINVAL;
 	else {
+		bzero(&uc, sizeof(uc));
 		get_mcontext32(td, &uc.uc_mcontext, GET_MC_CLEAR_RET);
 		PROC_LOCK(td->td_proc);
 		uc.uc_sigmask = td->td_sigmask;