vhost: fix info leak due to uninitialized memory (CVE-2018-1118)

debian/changelog

@@ -11,6 +11,7 @@ linux (4.17.2-1) UNRELEASED; urgency=medium
   * [mips*] Increase RELOCATION_TABLE_SIZE to 0x00140000 (fixes FTBFS)
   * Set ABI to 1
   * [x86,arm64] Disable code signing for upload to unstable
+  * vhost: fix info leak due to uninitialized memory (CVE-2018-1118)
 
   [ Romain Perier ]
   * [x86] Enable DCN 1.0 Raven family (Closes #901349)

debian/patches/bugfix/all/vhost-fix-info-leak-due-to-uninitialized-memory.patch

@@ -0,0 +1,36 @@
+From: "Michael S. Tsirkin" <mst@redhat.com>
+Date: Sat, 12 May 2018 00:33:10 +0300
+Subject: vhost: fix info leak due to uninitialized memory
+Origin: https://git.kernel.org/linus/670ae9caaca467ea1bfd325cb2a5c98ba87f94ad
+Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-1118
+
+struct vhost_msg within struct vhost_msg_node is copied to userspace.
+Unfortunately it turns out on 64 bit systems vhost_msg has padding after
+type which gcc doesn't initialize, leaking 4 uninitialized bytes to
+userspace.
+
+This padding also unfortunately means 32 bit users of this interface are
+broken on a 64 bit kernel which will need to be fixed separately.
+
+Fixes: CVE-2018-1118
+Cc: stable@vger.kernel.org
+Reported-by: Kevin Easton <kevin@guarana.org>
+Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
+Reported-by: syzbot+87cfa083e727a224754b@syzkaller.appspotmail.com
+Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
+---
+ drivers/vhost/vhost.c | 3 +++
+ 1 file changed, 3 insertions(+)
+
+--- a/drivers/vhost/vhost.c
++++ b/drivers/vhost/vhost.c
+@@ -2345,6 +2345,9 @@ struct vhost_msg_node *vhost_new_msg(str
+ 	struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
+ 	if (!node)
+ 		return NULL;
++
++	/* Make sure all padding within the structure is initialized. */
++	memset(&node->msg, 0, sizeof node->msg);
+ 	node->vq = vq;
+ 	node->msg.type = type;
+ 	return node;

debian/patches/series

@@ -125,6 +125,7 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
 
 # Security fixes
 debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
+bugfix/all/vhost-fix-info-leak-due-to-uninitialized-memory.patch
 
 # Fix exported symbol versions
 bugfix/all/module-disable-matching-missing-version-crc.patch