Merge remote-tracking branch 'remotes/otubo/tags/pull-seccomp-20180823' into staging

pull-seccomp-20180823

# gpg: Signature made Thu 23 Aug 2018 15:46:13 BST
# gpg:                using RSA key DF32E7C0F0FFF9A2
# gpg: Good signature from "Eduardo Otubo (Senior Software Engineer) <otubo@redhat.com>"
# Primary key fingerprint: D67E 1B50 9374 86B4 0723  DBAB DF32 E7C0 F0FF F9A2

* remotes/otubo/tags/pull-seccomp-20180823:
  seccomp: set the seccomp filter to all threads
  configure: require libseccomp 2.2.0
  seccomp: prefer SCMP_ACT_KILL_PROCESS if available
  seccomp: use SIGSYS signal instead of killing the thread

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 37 insertions, 6 deletions

diff --git a/configure b/configure
index 2ff272de79..58862d2ae8 100755
--- a/configure
+++ b/configure
@@ -2228,13 +2228,10 @@ fi
 ##########################################
 # libseccomp check
 
+libseccomp_minver="2.2.0"
 if test "$seccomp" != "no" ; then
     case "$cpu" in
-    i386|x86_64)
-        libseccomp_minver="2.1.0"
-        ;;
-    mips)
-        libseccomp_minver="2.2.0"
+    i386|x86_64|mips)
         ;;
     arm|aarch64)
         libseccomp_minver="2.2.3"
diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 9cd8eb9499..4729eb107f 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -20,6 +20,7 @@
 #include <sys/prctl.h>
 #include <seccomp.h>
 #include "sysemu/seccomp.h"
+#include <linux/seccomp.h>
 
 /* For some architectures (notably ARM) cacheflush is not supported until
  * libseccomp 2.2.3, but configure enforces that we are using a more recent
@@ -107,12 +108,40 @@ static const struct QemuSeccompSyscall blacklist[] = {
     { SCMP_SYS(sched_get_priority_min), QEMU_SECCOMP_SET_RESOURCECTL },
 };
 
+static inline __attribute__((unused)) int
+qemu_seccomp(unsigned int operation, unsigned int flags, void *args)
+{
+#ifdef __NR_seccomp
+    return syscall(__NR_seccomp, operation, flags, args);
+#else
+    errno = ENOSYS;
+    return -1;
+#endif
+}
+
+static uint32_t qemu_seccomp_get_kill_action(void)
+{
+#if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \
+    defined(SECCOMP_RET_KILL_PROCESS)
+    {
+        uint32_t action = SECCOMP_RET_KILL_PROCESS;
+
+        if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) {
+            return SCMP_ACT_KILL_PROCESS;
+        }
+    }
+#endif
+
+    return SCMP_ACT_TRAP;
+}
+
 
 static int seccomp_start(uint32_t seccomp_opts)
 {
     int rc = 0;
     unsigned int i = 0;
     scmp_filter_ctx ctx;
+    uint32_t action = qemu_seccomp_get_kill_action();
 
     ctx = seccomp_init(SCMP_ACT_ALLOW);
     if (ctx == NULL) {
@@ -120,12 +149,17 @@ static int seccomp_start(uint32_t seccomp_opts)
         goto seccomp_return;
     }
 
+    rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1);
+    if (rc != 0) {
+        goto seccomp_return;
+    }
+
     for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
         if (!(seccomp_opts & blacklist[i].set)) {
             continue;
         }
 
-        rc = seccomp_rule_add_array(ctx, SCMP_ACT_KILL, blacklist[i].num,
+        rc = seccomp_rule_add_array(ctx, action, blacklist[i].num,
                                     blacklist[i].narg, blacklist[i].arg_cmp);
         if (rc < 0) {
             goto seccomp_return;