system: Rename softmmu/ directory as system/

The softmmu/ directory contains files specific to system
emulation. Rename it as system/. Update meson rules, the
MAINTAINERS file and all the documentation and comments.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004090629.37473-14-philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 486 insertions, 0 deletions

diff --git a/system/qemu-seccomp.c b/system/qemu-seccomp.c
new file mode 100644
index 0000000000..4d7439e7f7
--- /dev/null
+++ b/system/qemu-seccomp.c
@@ -0,0 +1,486 @@
+/*
+ * QEMU seccomp mode 2 support with libseccomp
+ *
+ * Copyright IBM, Corp. 2012
+ *
+ * Authors:
+ *  Eduardo Otubo    <eotubo@br.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qemu/config-file.h"
+#include "qemu/option.h"
+#include "qemu/module.h"
+#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
+ * version on those hosts, so it is OK for this check to be less strict.
+ */
+#if SCMP_VER_MAJOR >= 3
+  #define HAVE_CACHEFLUSH
+#elif SCMP_VER_MAJOR == 2 && SCMP_VER_MINOR >= 2
+  #define HAVE_CACHEFLUSH
+#endif
+
+struct QemuSeccompSyscall {
+    int32_t num;
+    uint8_t set;
+    uint8_t narg;
+    const struct scmp_arg_cmp *arg_cmp;
+    uint32_t action;
+};
+
+const struct scmp_arg_cmp sched_setscheduler_arg[] = {
+    /* was SCMP_A1(SCMP_CMP_NE, SCHED_IDLE), but expanded due to GCC 4.x bug */
+    { .arg = 1, .op = SCMP_CMP_NE, .datum_a = SCHED_IDLE }
+};
+
+/*
+ * See 'NOTES' in 'man 2 clone' - s390 & cross have 'flags' in
+ *  different position to other architectures
+ */
+#if defined(HOST_S390X) || defined(HOST_S390) || defined(HOST_CRIS)
+#define CLONE_FLAGS_ARG 1
+#else
+#define CLONE_FLAGS_ARG 0
+#endif
+
+#ifndef CLONE_PIDFD
+# define CLONE_PIDFD 0x00001000
+#endif
+
+#define REQUIRE_CLONE_FLAG(flag) \
+    const struct scmp_arg_cmp clone_arg ## flag[] = { \
+    { .arg = CLONE_FLAGS_ARG, \
+      .op = SCMP_CMP_MASKED_EQ, \
+      .datum_a = flag, .datum_b = 0 } }
+
+#define FORBID_CLONE_FLAG(flag) \
+    const struct scmp_arg_cmp clone_arg ## flag[] = { \
+    { .arg = CLONE_FLAGS_ARG, \
+      .op = SCMP_CMP_MASKED_EQ, \
+      .datum_a = flag, .datum_b = flag } }
+
+#define RULE_CLONE_FLAG(flag) \
+    { SCMP_SYS(clone),                  QEMU_SECCOMP_SET_SPAWN, \
+      ARRAY_SIZE(clone_arg ## flag), clone_arg ## flag, SCMP_ACT_TRAP }
+
+/* If no CLONE_* flags are set, except CSIGNAL, deny */
+const struct scmp_arg_cmp clone_arg_none[] = {
+    { .arg = CLONE_FLAGS_ARG,
+      .op = SCMP_CMP_MASKED_EQ,
+      .datum_a = ~(CSIGNAL), .datum_b = 0 }
+};
+
+/*
+ * pthread_create should always set all of these.
+ */
+REQUIRE_CLONE_FLAG(CLONE_VM);
+REQUIRE_CLONE_FLAG(CLONE_FS);
+REQUIRE_CLONE_FLAG(CLONE_FILES);
+REQUIRE_CLONE_FLAG(CLONE_SIGHAND);
+REQUIRE_CLONE_FLAG(CLONE_THREAD);
+REQUIRE_CLONE_FLAG(CLONE_SYSVSEM);
+REQUIRE_CLONE_FLAG(CLONE_SETTLS);
+REQUIRE_CLONE_FLAG(CLONE_PARENT_SETTID);
+REQUIRE_CLONE_FLAG(CLONE_CHILD_CLEARTID);
+/*
+ * Musl sets this in pthread_create too, but it is
+ * obsolete and harmless since its behaviour is
+ * subsumed under CLONE_THREAD
+ */
+/*REQUIRE_CLONE_FLAG(CLONE_DETACHED);*/
+
+
+/*
+ * These all indicate an attempt to spawn a process
+ * instead of a thread, or other undesirable scenarios
+ */
+FORBID_CLONE_FLAG(CLONE_PIDFD);
+FORBID_CLONE_FLAG(CLONE_PTRACE);
+FORBID_CLONE_FLAG(CLONE_VFORK);
+FORBID_CLONE_FLAG(CLONE_PARENT);
+FORBID_CLONE_FLAG(CLONE_NEWNS);
+FORBID_CLONE_FLAG(CLONE_UNTRACED);
+FORBID_CLONE_FLAG(CLONE_NEWCGROUP);
+FORBID_CLONE_FLAG(CLONE_NEWUTS);
+FORBID_CLONE_FLAG(CLONE_NEWIPC);
+FORBID_CLONE_FLAG(CLONE_NEWUSER);
+FORBID_CLONE_FLAG(CLONE_NEWPID);
+FORBID_CLONE_FLAG(CLONE_NEWNET);
+FORBID_CLONE_FLAG(CLONE_IO);
+
+
+static const struct QemuSeccompSyscall denylist[] = {
+    /* default set of syscalls that should get blocked */
+    { 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,
+      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,
+      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,
+      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 },
+    { SCMP_SYS(clone),                  QEMU_SECCOMP_SET_SPAWN,
+      ARRAY_SIZE(clone_arg_none), clone_arg_none, SCMP_ACT_TRAP },
+    RULE_CLONE_FLAG(CLONE_VM),
+    RULE_CLONE_FLAG(CLONE_FS),
+    RULE_CLONE_FLAG(CLONE_FILES),
+    RULE_CLONE_FLAG(CLONE_SIGHAND),
+    RULE_CLONE_FLAG(CLONE_THREAD),
+    RULE_CLONE_FLAG(CLONE_SYSVSEM),
+    RULE_CLONE_FLAG(CLONE_SETTLS),
+    RULE_CLONE_FLAG(CLONE_PARENT_SETTID),
+    RULE_CLONE_FLAG(CLONE_CHILD_CLEARTID),
+    /*RULE_CLONE_FLAG(CLONE_DETACHED),*/
+    RULE_CLONE_FLAG(CLONE_PIDFD),
+    RULE_CLONE_FLAG(CLONE_PTRACE),
+    RULE_CLONE_FLAG(CLONE_VFORK),
+    RULE_CLONE_FLAG(CLONE_PARENT),
+    RULE_CLONE_FLAG(CLONE_NEWNS),
+    RULE_CLONE_FLAG(CLONE_UNTRACED),
+    RULE_CLONE_FLAG(CLONE_NEWCGROUP),
+    RULE_CLONE_FLAG(CLONE_NEWUTS),
+    RULE_CLONE_FLAG(CLONE_NEWIPC),
+    RULE_CLONE_FLAG(CLONE_NEWUSER),
+    RULE_CLONE_FLAG(CLONE_NEWPID),
+    RULE_CLONE_FLAG(CLONE_NEWNET),
+    RULE_CLONE_FLAG(CLONE_IO),
+#ifdef __SNR_clone3
+    { SCMP_SYS(clone3),                 QEMU_SECCOMP_SET_SPAWN,
+      0, NULL, SCMP_ACT_ERRNO(ENOSYS) },
+#endif
+#ifdef __SNR_execveat
+    { SCMP_SYS(execveat),               QEMU_SECCOMP_SET_SPAWN },
+#endif
+    { SCMP_SYS(setns),                  QEMU_SECCOMP_SET_SPAWN },
+    { SCMP_SYS(unshare),                QEMU_SECCOMP_SET_SPAWN },
+    /* resource control */
+    { 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_ACT_ERRNO(EPERM) },
+    { SCMP_SYS(sched_setaffinity),      QEMU_SECCOMP_SET_RESOURCECTL,
+      0, NULL, SCMP_ACT_ERRNO(EPERM) },
+};
+
+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_update_action(uint32_t action)
+{
+#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 testaction = SECCOMP_RET_KILL_PROCESS;
+
+            if (qemu_seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &testaction) == 0) {
+                kill_process = 1;
+            } else {
+                kill_process = 0;
+            }
+        }
+        if (kill_process == 1) {
+            return SCMP_ACT_KILL_PROCESS;
+        }
+    }
+#endif
+    return action;
+}
+
+
+static int seccomp_start(uint32_t seccomp_opts, Error **errp)
+{
+    int rc = -1;
+    unsigned int i = 0;
+    scmp_filter_ctx ctx;
+
+    ctx = seccomp_init(SCMP_ACT_ALLOW);
+    if (ctx == NULL) {
+        error_setg(errp, "failed to initialize seccomp context");
+        goto seccomp_return;
+    }
+
+#if defined(CONFIG_SECCOMP_SYSRAWRC)
+    /*
+     * This must be the first seccomp_attr_set() call to have full
+     * error propagation from subsequent seccomp APIs.
+     */
+    rc = seccomp_attr_set(ctx, SCMP_FLTATR_API_SYSRAWRC, 1);
+    if (rc != 0) {
+        error_setg_errno(errp, -rc,
+                         "failed to set seccomp rawrc attribute");
+        goto seccomp_return;
+    }
+#endif
+
+    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(denylist); i++) {
+        uint32_t action;
+        if (!(seccomp_opts & denylist[i].set)) {
+            continue;
+        }
+
+        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) {
+            error_setg_errno(errp, -rc,
+                             "failed to add seccomp denylist 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 < 0 ? -1 : 0;
+}
+
+int parse_sandbox(void *opaque, QemuOpts *opts, Error **errp)
+{
+    if (qemu_opt_get_bool(opts, "enable", false)) {
+        uint32_t seccomp_opts = QEMU_SECCOMP_SET_DEFAULT
+                | QEMU_SECCOMP_SET_OBSOLETE;
+        const char *value = NULL;
+
+        value = qemu_opt_get(opts, "obsolete");
+        if (value) {
+            if (g_str_equal(value, "allow")) {
+                seccomp_opts &= ~QEMU_SECCOMP_SET_OBSOLETE;
+            } else if (g_str_equal(value, "deny")) {
+                /* this is the default option, this if is here
+                 * to provide a little bit of consistency for
+                 * the command line */
+            } else {
+                error_setg(errp, "invalid argument for obsolete");
+                return -1;
+            }
+        }
+
+        value = qemu_opt_get(opts, "elevateprivileges");
+        if (value) {
+            if (g_str_equal(value, "deny")) {
+                seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
+            } else if (g_str_equal(value, "children")) {
+                seccomp_opts |= QEMU_SECCOMP_SET_PRIVILEGED;
+
+                /* calling prctl directly because we're
+                 * not sure if host has CAP_SYS_ADMIN set*/
+                if (prctl(PR_SET_NO_NEW_PRIVS, 1)) {
+                    error_setg(errp, "failed to set no_new_privs aborting");
+                    return -1;
+                }
+            } else if (g_str_equal(value, "allow")) {
+                /* default value */
+            } else {
+                error_setg(errp, "invalid argument for elevateprivileges");
+                return -1;
+            }
+        }
+
+        value = qemu_opt_get(opts, "spawn");
+        if (value) {
+            if (g_str_equal(value, "deny")) {
+                seccomp_opts |= QEMU_SECCOMP_SET_SPAWN;
+            } else if (g_str_equal(value, "allow")) {
+                /* default value */
+            } else {
+                error_setg(errp, "invalid argument for spawn");
+                return -1;
+            }
+        }
+
+        value = qemu_opt_get(opts, "resourcecontrol");
+        if (value) {
+            if (g_str_equal(value, "deny")) {
+                seccomp_opts |= QEMU_SECCOMP_SET_RESOURCECTL;
+            } else if (g_str_equal(value, "allow")) {
+                /* default value */
+            } else {
+                error_setg(errp, "invalid argument for resourcecontrol");
+                return -1;
+            }
+        }
+
+        if (seccomp_start(seccomp_opts, errp) < 0) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static QemuOptsList qemu_sandbox_opts = {
+    .name = "sandbox",
+    .implied_opt_name = "enable",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_sandbox_opts.head),
+    .desc = {
+        {
+            .name = "enable",
+            .type = QEMU_OPT_BOOL,
+        },
+        {
+            .name = "obsolete",
+            .type = QEMU_OPT_STRING,
+        },
+        {
+            .name = "elevateprivileges",
+            .type = QEMU_OPT_STRING,
+        },
+        {
+            .name = "spawn",
+            .type = QEMU_OPT_STRING,
+        },
+        {
+            .name = "resourcecontrol",
+            .type = QEMU_OPT_STRING,
+        },
+        { /* end of list */ }
+    },
+};
+
+static void seccomp_register(void)
+{
+    bool add = false;
+
+    /* FIXME: use seccomp_api_get() >= 2 check when released */
+
+#if defined(SECCOMP_FILTER_FLAG_TSYNC)
+    int check;
+
+    /* check host TSYNC capability, it returns errno == ENOSYS if unavailable */
+    check = qemu_seccomp(SECCOMP_SET_MODE_FILTER,
+                         SECCOMP_FILTER_FLAG_TSYNC, NULL);
+    if (check < 0 && errno == EFAULT) {
+        add = true;
+    }
+#endif
+
+    if (add) {
+        qemu_add_opts(&qemu_sandbox_opts);
+    }
+}
+opts_init(seccomp_register);