From 78152453940967f9ece9fe3ffc5017c669d6ec28 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Tue, 5 May 2020 16:36:00 +0100
Subject: [PATCH 9/9] virtiofsd: drop all capabilities in the wait parent
 process
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20200505163600.22956-8-dgilbert@redhat.com>
Patchwork-id: 96274
O-Subject: [RHEL-AV-8.2.1 qemu-kvm PATCH 7/7] virtiofsd: drop all capabilities in the wait parent process
Bugzilla: 1817445
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Philippe Mathieu-Daudé <philmd@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>

From: Stefan Hajnoczi <stefanha@redhat.com>

All this process does is wait for its child.  No capabilities are
needed.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
(cherry picked from commit 66502bbca37ca7a3bfa57e82cfc03b89a7a11eae)
Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
---
 tools/virtiofsd/passthrough_ll.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 6358874..f41a6b0 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -2535,6 +2535,17 @@ static void print_capabilities(void)
 }
 
 /*
+ * Drop all Linux capabilities because the wait parent process only needs to
+ * sit in waitpid(2) and terminate.
+ */
+static void setup_wait_parent_capabilities(void)
+{
+    capng_setpid(syscall(SYS_gettid));
+    capng_clear(CAPNG_SELECT_BOTH);
+    capng_apply(CAPNG_SELECT_BOTH);
+}
+
+/*
  * Move to a new mount, net, and pid namespaces to isolate this process.
  */
 static void setup_namespaces(struct lo_data *lo, struct fuse_session *se)
@@ -2567,6 +2578,8 @@ static void setup_namespaces(struct lo_data *lo, struct fuse_session *se)
         pid_t waited;
         int wstatus;
 
+        setup_wait_parent_capabilities();
+
         /* The parent waits for the child */
         do {
             waited = waitpid(child, &wstatus, 0);
-- 
1.8.3.1