Merge remote-tracking branch 'remotes/otubo/tags/pull-seccomp-20190327' into staging

pull-seccomp-20190327

# gpg: Signature made Wed 27 Mar 2019 12:12:39 GMT
# gpg:                using RSA key DF32E7C0F0FFF9A2
# gpg: Good signature from "Eduardo Otubo (Senior Software Engineer) <otubo@redhat.com>" [full]
# Primary key fingerprint: D67E 1B50 9374 86B4 0723  DBAB DF32 E7C0 F0FF F9A2

* remotes/otubo/tags/pull-seccomp-20190327:
  seccomp: report more useful errors from seccomp
  seccomp: don't kill process for resource control syscalls

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

1 files changed, 38 insertions, 14 deletions

diff --git a/qemu-seccomp.c b/qemu-seccomp.c
index 36d5829831..e0a1829b3d 100644
--- a/qemu-seccomp.c
+++ b/qemu-seccomp.c
@@ -121,58 +121,84 @@ qemu_seccomp(unsigned int operation, unsigned int flags, void *args)
 #endif
 }
 
-static uint32_t qemu_seccomp_get_kill_action(void)
+static uint32_t qemu_seccomp_get_action(int set)
 {
+    switch (set) {
+    case QEMU_SECCOMP_SET_DEFAULT:
+    case QEMU_SECCOMP_SET_OBSOLETE:
+    case QEMU_SECCOMP_SET_PRIVILEGED:
+    case QEMU_SECCOMP_SET_SPAWN: {
 #if defined(SECCOMP_GET_ACTION_AVAIL) && defined(SCMP_ACT_KILL_PROCESS) && \
     defined(SECCOMP_RET_KILL_PROCESS)
-    {
-        uint32_t action = SECCOMP_RET_KILL_PROCESS;
+        static int kill_process = -1;
+        if (kill_process == -1) {
+            uint32_t action = SECCOMP_RET_KILL_PROCESS;
 
-        if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) {
+            if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &action) == 0) {
+                kill_process = 1;
+            }
+            kill_process = 0;
+        }
+        if (kill_process == 1) {
             return SCMP_ACT_KILL_PROCESS;
         }
-    }
 #endif
+        return SCMP_ACT_TRAP;
+    }
 
-    return SCMP_ACT_TRAP;
+    case QEMU_SECCOMP_SET_RESOURCECTL:
+        return SCMP_ACT_ERRNO(EPERM);
+
+    default:
+        g_assert_not_reached();
+    }
 }
 
 
-static int seccomp_start(uint32_t seccomp_opts)
+static int seccomp_start(uint32_t seccomp_opts, Error **errp)
 {
-    int rc = 0;
+    int rc = -1;
     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) {
-        rc = -1;
+        error_setg(errp, "failed to initialize seccomp context");
         goto seccomp_return;
     }
 
     rc = seccomp_attr_set(ctx, SCMP_FLTATR_CTL_TSYNC, 1);
     if (rc != 0) {
+        error_setg_errno(errp, -rc,
+                         "failed to set seccomp thread synchronization");
         goto seccomp_return;
     }
 
     for (i = 0; i < ARRAY_SIZE(blacklist); i++) {
+        uint32_t action;
         if (!(seccomp_opts & blacklist[i].set)) {
             continue;
         }
 
+        action = qemu_seccomp_get_action(blacklist[i].set);
         rc = seccomp_rule_add_array(ctx, action, blacklist[i].num,
                                     blacklist[i].narg, blacklist[i].arg_cmp);
         if (rc < 0) {
+            error_setg_errno(errp, -rc,
+                             "failed to add seccomp blacklist rules");
             goto seccomp_return;
         }
     }
 
     rc = seccomp_load(ctx);
+    if (rc < 0) {
+        error_setg_errno(errp, -rc,
+                         "failed to load seccomp syscall filter in kernel");
+    }
 
   seccomp_return:
     seccomp_release(ctx);
-    return rc;
+    return rc < 0 ? -1 : 0;
 }
 
 #ifdef CONFIG_SECCOMP
@@ -242,9 +268,7 @@ int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
             }
         }
 
-        if (seccomp_start(seccomp_opts) < 0) {
-            error_setg(errp, "failed to install seccomp syscall filter "
-                       "in the kernel");
+        if (seccomp_start(seccomp_opts, errp) < 0) {
             return -1;
         }
     }