seccomp: allow action to be customized per syscall

We're currently tailoring whether to use kill process or return EPERM
based on the syscall set. This is not flexible enough for future
requirements where we also need to be able to return a variety of
actions on a per-syscall granularity.

Acked-by: Eduardo Otubo <otubo@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

1 files changed, 106 insertions, 66 deletions

diff --git a/softmmu/qemu-seccomp.c b/softmmu/qemu-seccomp.c
index f500267..9f6df8d 100644
--- a/softmmu/qemu-seccomp.c
+++ b/softmmu/qemu-seccomp.c
@@ -38,6 +38,7 @@ struct QemuSeccompSyscall {
     uint8_t set;
     uint8_t narg;
     const struct scmp_arg_cmp *arg_cmp;
+    uint32_t action;
 };
 
 const struct scmp_arg_cmp sched_setscheduler_arg[] = {
@@ -47,61 +48,111 @@ const struct scmp_arg_cmp sched_setscheduler_arg[] = {
 
 static const struct QemuSeccompSyscall denylist[] = {
     /* default set of syscalls that should get blocked */
-    { SCMP_SYS(reboot),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(swapon),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(swapoff),                QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(syslog),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(mount),                  QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(umount),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(kexec_load),             QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(afs_syscall),            QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(break),                  QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(ftime),                  QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(getpmsg),                QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(gtty),                   QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(lock),                   QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(mpx),                    QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(prof),                   QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(profil),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(putpmsg),                QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(security),               QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(stty),                   QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(tuxcall),                QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(ulimit),                 QEMU_SECCOMP_SET_DEFAULT },
-    { SCMP_SYS(vserver),                QEMU_SECCOMP_SET_DEFAULT },
+    { SCMP_SYS(reboot),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(swapon),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(swapoff),                QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(syslog),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(mount),                  QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(umount),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(kexec_load),             QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(afs_syscall),            QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(break),                  QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(ftime),                  QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(getpmsg),                QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(gtty),                   QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(lock),                   QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(mpx),                    QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(prof),                   QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(profil),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(putpmsg),                QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(security),               QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(stty),                   QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(tuxcall),                QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(ulimit),                 QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(vserver),                QEMU_SECCOMP_SET_DEFAULT,
+      0, NULL, SCMP_ACT_TRAP },
     /* obsolete */
-    { SCMP_SYS(readdir),                QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(_sysctl),                QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(bdflush),                QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(create_module),          QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(get_kernel_syms),        QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(query_module),           QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(sgetmask),               QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(ssetmask),               QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(sysfs),                  QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(uselib),                 QEMU_SECCOMP_SET_OBSOLETE },
-    { SCMP_SYS(ustat),                  QEMU_SECCOMP_SET_OBSOLETE },
+    { SCMP_SYS(readdir),                QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(_sysctl),                QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(bdflush),                QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(create_module),          QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(get_kernel_syms),        QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(query_module),           QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(sgetmask),               QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(ssetmask),               QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(sysfs),                  QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(uselib),                 QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(ustat),                  QEMU_SECCOMP_SET_OBSOLETE,
+      0, NULL, SCMP_ACT_TRAP },
     /* privileged */
-    { SCMP_SYS(setuid),                 QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setgid),                 QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setpgid),                QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setsid),                 QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setreuid),               QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setregid),               QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setresuid),              QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setresgid),              QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setfsuid),               QEMU_SECCOMP_SET_PRIVILEGED },
-    { SCMP_SYS(setfsgid),               QEMU_SECCOMP_SET_PRIVILEGED },
+    { SCMP_SYS(setuid),                 QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setgid),                 QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setpgid),                QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setsid),                 QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setreuid),               QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setregid),               QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setresuid),              QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setresgid),              QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setfsuid),               QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(setfsgid),               QEMU_SECCOMP_SET_PRIVILEGED,
+      0, NULL, SCMP_ACT_TRAP },
     /* spawn */
-    { SCMP_SYS(fork),                   QEMU_SECCOMP_SET_SPAWN },
-    { SCMP_SYS(vfork),                  QEMU_SECCOMP_SET_SPAWN },
-    { SCMP_SYS(execve),                 QEMU_SECCOMP_SET_SPAWN },
+    { SCMP_SYS(fork),                   QEMU_SECCOMP_SET_SPAWN,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(vfork),                  QEMU_SECCOMP_SET_SPAWN,
+      0, NULL, SCMP_ACT_TRAP },
+    { SCMP_SYS(execve),                 QEMU_SECCOMP_SET_SPAWN,
+      0, NULL, SCMP_ACT_TRAP },
     /* resource control */
-    { SCMP_SYS(setpriority),            QEMU_SECCOMP_SET_RESOURCECTL },
-    { SCMP_SYS(sched_setparam),         QEMU_SECCOMP_SET_RESOURCECTL },
+    { SCMP_SYS(setpriority),            QEMU_SECCOMP_SET_RESOURCECTL,
+      0, NULL, SCMP_ACT_ERRNO(EPERM) },
+    { SCMP_SYS(sched_setparam),         QEMU_SECCOMP_SET_RESOURCECTL,
+      0, NULL, SCMP_ACT_ERRNO(EPERM) },
     { SCMP_SYS(sched_setscheduler),     QEMU_SECCOMP_SET_RESOURCECTL,
-      ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg },
-    { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL },
+      ARRAY_SIZE(sched_setscheduler_arg), sched_setscheduler_arg,
+      SCMP_ACT_ERRNO(EPERM) },
+    { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL,
+      0, NULL, SCMP_ACT_ERRNO(EPERM) },
 };
 
 static inline __attribute__((unused)) int
@@ -115,15 +166,11 @@ qemu_seccomp(unsigned int operation, unsigned int flags, void *args)
 #endif
 }
 
-static uint32_t qemu_seccomp_get_action(int set)
+static uint32_t qemu_seccomp_update_action(uint32_t action)
 {
-    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)
+    if (action == SCMP_ACT_TRAP) {
         static int kill_process = -1;
         if (kill_process == -1) {
             uint32_t action = SECCOMP_RET_KILL_PROCESS;
@@ -137,16 +184,9 @@ static uint32_t qemu_seccomp_get_action(int set)
         if (kill_process == 1) {
             return SCMP_ACT_KILL_PROCESS;
         }
-#endif
-        return SCMP_ACT_TRAP;
-    }
-
-    case QEMU_SECCOMP_SET_RESOURCECTL:
-        return SCMP_ACT_ERRNO(EPERM);
-
-    default:
-        g_assert_not_reached();
     }
+#endif
+    return action;
 }
 
 
@@ -175,7 +215,7 @@ static int seccomp_start(uint32_t seccomp_opts, Error **errp)
             continue;
         }
 
-        action = qemu_seccomp_get_action(denylist[i].set);
+        action = qemu_seccomp_update_action(denylist[i].action);
         rc = seccomp_rule_add_array(ctx, action, denylist[i].num,
                                     denylist[i].narg, denylist[i].arg_cmp);
         if (rc < 0) {