[Qemu-devel] [PATCHv3 2/3] seccomp: adding command line support for blacklist

[Eduardo Otubo <otubo@linux.vnet.ibm.com>]

v3: The options for blacklist in the command line also checkes the
existence of "-netdev tap", leaving a warning message in a positive
case.

New command line options for the seccomp blacklist feature:

 $ qemu -sandbox on[,strict=<on|off>]

The strict parameter will turn on or off the new system call blacklist

Signed-off-by: Eduardo Otubo <otubo@linux.vnet.ibm.com>
---
 qemu-options.hx |  8 +++++---
 vl.c            | 17 ++++++++++++++++-
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index d15338e..05485e1 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2978,13 +2978,15 @@ Old param mode (ARM only).
 ETEXI
 
 DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \
-    "-sandbox <arg>  Enable seccomp mode 2 system call filter (default 'off').\n",
+    "-sandbox <arg>  Enable seccomp mode 2 system call filter (default 'off').\n"
+    "-sandbox on[,strict=<arg>]\n"
+    "                Enable seccomp mode 2 system call second level filter (default 'off').\n",
     QEMU_ARCH_ALL)
 STEXI
-@item -sandbox @var{arg}
+@item -sandbox @var{arg}[,strict=@var{value}]
 @findex -sandbox
 Enable Seccomp mode 2 system call filter. 'on' will enable syscall filtering and 'off' will
-disable it.  The default is 'off'.
+disable it.  The default is 'off'. 'strict=on' will enable second level filter (default is 'off').
 ETEXI
 
 DEF("readconfig", HAS_ARG, QEMU_OPTION_readconfig,
diff --git a/vl.c b/vl.c
index ee95674..ffdf460 100644
--- a/vl.c
+++ b/vl.c
@@ -330,6 +330,9 @@ static QemuOptsList qemu_sandbox_opts = {
         {
             .name = "enable",
             .type = QEMU_OPT_BOOL,
+        },{
+            .name = "strict",
+            .type = QEMU_OPT_STRING,
         },
         { /* end of list */ }
     },
@@ -1032,6 +1035,7 @@ static int bt_parse(const char *opt)
 
 static int parse_sandbox(QemuOpts *opts, void *opaque)
 {
+    const char *strict_value = NULL;
     /* FIXME: change this to true for 1.3 */
     if (qemu_opt_get_bool(opts, "enable", false)) {
 #ifdef CONFIG_SECCOMP
@@ -1040,6 +1044,17 @@ static int parse_sandbox(QemuOpts *opts, void *opaque)
                           "failed to install seccomp syscall filter in the kernel");
             return -1;
         }
+
+        strict_value = qemu_opt_get(opts, "strict");
+
+        if (!tap_enabled)
+           if (strict_value && !strcmp(strict_value, "on")) {
+               enable_blacklist = true;
+           }
+        } else {
+            fprintf(stderr, "Warning: seccomp syscall second level filter \"-sandbox on,strict=on\" "
+                    "cannot work together with \"-netdev tap\". Disabling it.\n");
+        }
 #else
         qerror_report(ERROR_CLASS_GENERIC_ERROR,
                       "sandboxing request but seccomp is not compiled into this build");
@@ -1769,7 +1784,7 @@ void vm_state_notify(int running, RunState state)
 
 static void install_seccomp_blacklist(void)
 {
-    if (enable_blacklist && !tap_enabled) {
+    if (enable_blacklist) {
         if (seccomp_start(BLACKLIST) < 0) {
             qerror_report(ERROR_CLASS_GENERIC_ERROR,
                           "failed to install seccomp syscall second level filter in the kernel");
-- 
1.8.3.1