Migration and virtiofs pull 2021-07-01 v2

Dropped Peter Xu's migration-test fix to reenable
 most of the migration tests when uffd isn't available;
 we're seeing at least one seg in github CI (on qemu-system-i386)
 and Peter Maydell is reporting a hang on Openbsd.
 
 Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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Merge remote-tracking branch 'remotes/dgilbert-gitlab/tags/pull-migration-20210705a' into staging

Migration and virtiofs pull 2021-07-01 v2

Dropped Peter Xu's migration-test fix to reenable
most of the migration tests when uffd isn't available;
we're seeing at least one seg in github CI (on qemu-system-i386)
and Peter Maydell is reporting a hang on Openbsd.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

# gpg: Signature made Mon 05 Jul 2021 11:01:35 BST
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert-gitlab/tags/pull-migration-20210705a:
  migration/rdma: Use error_report to suppress errno message
  tests/migration: fix "downtime_limit" type when "migrate-set-parameters"
  tests/migration: parse the thread-id key of CpuInfoFast
  virtiofsd: Add an option to enable/disable posix acls
  virtiofsd: Switch creds, drop FSETID for system.posix_acl_access xattr
  virtiofsd: Add capability to change/restore umask
  virtiofsd: Add umask to seccom allow list
  virtiofsd: Add support for extended setxattr
  virtiofsd: Fix xattr operations overwriting errno
  virtiofsd: Fix fuse setxattr() API change issue
  virtiofsd: Don't allow file creation with FUSE_OPEN
  docs: describe the security considerations with virtiofsd xattr mapping
  virtiofsd: use GDateTime for formatting timestamp for debug messages
  migration: failover: continue to wait card unplug on error
  migration: move wait-unplug loop to its own function
  migration: Allow reset of postcopy_recover_triggered when failed
  migration: Move yank outside qemu_start_incoming_migration()
  migration: fix the memory overwriting risk in add_to_iovec
  tests: migration-test: Add dirty ring test

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

docs/tools/virtiofsd.rst

@@ -101,6 +101,9 @@ Options
     Enable/disable extended attributes (xattr) on files and directories.  The
     default is ``no_xattr``.
 
+  * posix_acl|no_posix_acl -
+    Enable/disable posix acl support.  Posix ACLs are disabled by default`.
+
 .. option:: --socket-path=PATH
 
   Listen on vhost-user UNIX domain socket at PATH.
@@ -127,8 +130,8 @@ Options
   timeout.  ``always`` sets a long cache lifetime at the expense of coherency.
   The default is ``auto``.
 
-xattr-mapping
+Extended attribute (xattr) mapping
--------------
+----------------------------------
 
 By default the name of xattr's used by the client are passed through to the server
 file system.  This can be a problem where either those xattr names are used
@@ -136,6 +139,9 @@ by something on the server (e.g. selinux client/server confusion) or if the
 virtiofsd is running in a container with restricted privileges where it cannot
 access some attributes.
 
+Mapping syntax
+~~~~~~~~~~~~~~
+
 A mapping of xattr names can be made using -o xattrmap=mapping where the ``mapping``
 string consists of a series of rules.
 
@@ -232,8 +238,48 @@ Note: When the 'security.capability' xattr is remapped, the daemon has to do
 extra work to remove it during many operations, which the host kernel normally
 does itself.
 
-xattr-mapping Examples
+Security considerations
-----------------------
+~~~~~~~~~~~~~~~~~~~~~~~
+
+Operating systems typically partition the xattr namespace using
+well defined name prefixes. Each partition may have different
+access controls applied. For example, on Linux there are multiple
+partitions
+
+ * ``system.*`` - access varies depending on attribute & filesystem
+ * ``security.*`` - only processes with CAP_SYS_ADMIN
+ * ``trusted.*`` - only processes with CAP_SYS_ADMIN
+ * ``user.*`` - any process granted by file permissions / ownership
+
+While other OS such as FreeBSD have different name prefixes
+and access control rules.
+
+When remapping attributes on the host, it is important to
+ensure that the remapping does not allow a guest user to
+evade the guest access control rules.
+
+Consider if ``trusted.*`` from the guest was remapped to
+``user.virtiofs.trusted*`` in the host. An unprivileged
+user in a Linux guest has the ability to write to xattrs
+under ``user.*``. Thus the user can evade the access
+control restriction on ``trusted.*`` by instead writing
+to ``user.virtiofs.trusted.*``.
+
+As noted above, the partitions used and access controls
+applied, will vary across guest OS, so it is not wise to
+try to predict what the guest OS will use.
+
+The simplest way to avoid an insecure configuration is
+to remap all xattrs at once, to a given fixed prefix.
+This is shown in example (1) below.
+
+If selectively mapping only a subset of xattr prefixes,
+then rules must be added to explicitly block direct
+access to the target of the remapping. This is shown
+in example (2) below.
+
+Mapping examples
+~~~~~~~~~~~~~~~~
 
 1) Prefix all attributes with 'user.virtiofs.'
 
@@ -271,7 +317,9 @@ stripping of 'user.virtiofs.'.
 The second rule hides unprefixed 'trusted.' attributes
 on the host.
 The third rule stops a guest from explicitly setting
-the 'user.virtiofs.' path directly.
+the 'user.virtiofs.' path directly to prevent access
+control bypass on the target of the earlier prefix
+remapping.
 Finally, the fourth rule lets all remaining attributes
 through.
 

migration/migration.c

@@ -456,10 +456,6 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
 {
     const char *p = NULL;
 
-    if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
-        return;
-    }
-
     qapi_event_send_migration(MIGRATION_STATUS_SETUP);
     if (strstart(uri, "tcp:", &p) ||
         strstart(uri, "unix:", NULL) ||
@@ -474,7 +470,6 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_incoming_migration(p, errp);
     } else {
-        yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         error_setg(errp, "unknown migration protocol: %s", uri);
     }
 }
@@ -2083,9 +2078,14 @@ void qmp_migrate_incoming(const char *uri, Error **errp)
         return;
     }
 
+    if (!yank_register_instance(MIGRATION_YANK_INSTANCE, errp)) {
+        return;
+    }
+
     qemu_start_incoming_migration(uri, &local_err);
 
     if (local_err) {
+        yank_unregister_instance(MIGRATION_YANK_INSTANCE);
         error_propagate(errp, local_err);
         return;
     }
@@ -2097,6 +2097,13 @@ void qmp_migrate_recover(const char *uri, Error **errp)
 {
     MigrationIncomingState *mis = migration_incoming_get_current();
 
+    /*
+     * Don't even bother to use ERRP_GUARD() as it _must_ always be set by
+     * callers (no one should ignore a recover failure); if there is, it's a
+     * programming error.
+     */
+    assert(errp);
+
     if (mis->state != MIGRATION_STATUS_POSTCOPY_PAUSED) {
         error_setg(errp, "Migrate recover can only be run "
                    "when postcopy is paused.");
@@ -2114,8 +2121,13 @@ void qmp_migrate_recover(const char *uri, Error **errp)
      * only re-setup the migration stream and poke existing migration
      * to continue using that newly established channel.
      */
-    yank_unregister_instance(MIGRATION_YANK_INSTANCE);
     qemu_start_incoming_migration(uri, errp);
+
+    /* Safe to dereference with the assert above */
+    if (*errp) {
+        /* Reset the flag so user could still retry */
+        qatomic_set(&mis->postcopy_recover_triggered, false);
+    }
 }
 
 void qmp_migrate_pause(Error **errp)
@@ -3664,6 +3676,39 @@ bool migration_rate_limit(void)
     return urgent;
 }
 
+/*
+ * if failover devices are present, wait they are completely
+ * unplugged
+ */
+
+static void qemu_savevm_wait_unplug(MigrationState *s, int old_state,
+                                    int new_state)
+{
+    if (qemu_savevm_state_guest_unplug_pending()) {
+        migrate_set_state(&s->state, old_state, MIGRATION_STATUS_WAIT_UNPLUG);
+
+        while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
+               qemu_savevm_state_guest_unplug_pending()) {
+            qemu_sem_timedwait(&s->wait_unplug_sem, 250);
+        }
+        if (s->state != MIGRATION_STATUS_WAIT_UNPLUG) {
+            int timeout = 120; /* 30 seconds */
+            /*
+             * migration has been canceled
+             * but as we have started an unplug we must wait the end
+             * to be able to plug back the card
+             */
+            while (timeout-- && qemu_savevm_state_guest_unplug_pending()) {
+                qemu_sem_timedwait(&s->wait_unplug_sem, 250);
+            }
+        }
+
+        migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG, new_state);
+    } else {
+        migrate_set_state(&s->state, old_state, new_state);
+    }
+}
+
 /*
  * Master migration thread on the source VM.
  * It drives the migration and pumps the data down the outgoing channel.
@@ -3710,22 +3755,10 @@ static void *migration_thread(void *opaque)
 
     qemu_savevm_state_setup(s->to_dst_file);
 
-    if (qemu_savevm_state_guest_unplug_pending()) {
+    qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
-        migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
+                               MIGRATION_STATUS_ACTIVE);
-                          MIGRATION_STATUS_WAIT_UNPLUG);
-
-        while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
-               qemu_savevm_state_guest_unplug_pending()) {
-            qemu_sem_timedwait(&s->wait_unplug_sem, 250);
-        }
-
-        migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG,
-                MIGRATION_STATUS_ACTIVE);
-    }
 
     s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
-    migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
-                      MIGRATION_STATUS_ACTIVE);
 
     trace_migration_thread_setup_complete();
 
@@ -3833,21 +3866,9 @@ static void *bg_migration_thread(void *opaque)
     qemu_savevm_state_header(s->to_dst_file);
     qemu_savevm_state_setup(s->to_dst_file);
 
-    if (qemu_savevm_state_guest_unplug_pending()) {
+    qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
-        migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
+                               MIGRATION_STATUS_ACTIVE);
-                          MIGRATION_STATUS_WAIT_UNPLUG);
 
-        while (s->state == MIGRATION_STATUS_WAIT_UNPLUG &&
-               qemu_savevm_state_guest_unplug_pending()) {
-            qemu_sem_timedwait(&s->wait_unplug_sem, 250);
-        }
-
-        migrate_set_state(&s->state, MIGRATION_STATUS_WAIT_UNPLUG,
-                          MIGRATION_STATUS_ACTIVE);
-    } else {
-        migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
-                MIGRATION_STATUS_ACTIVE);
-    }
     s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
 
     trace_migration_thread_setup_complete();

migration/qemu-file.c

@@ -416,6 +416,11 @@ static int add_to_iovec(QEMUFile *f, const uint8_t *buf, size_t size,
     {
         f->iov[f->iovcnt - 1].iov_len += size;
     } else {
+        if (f->iovcnt >= MAX_IOV_SIZE) {
+            /* Should only happen if a previous fflush failed */
+            assert(f->shutdown || !qemu_file_is_writable(f));
+            return 1;
+        }
         if (may_free) {
             set_bit(f->iovcnt, f->may_free);
         }

migration/rdma.c

@@ -1006,7 +1006,7 @@ route:
     if (cm_event->event != RDMA_CM_EVENT_ADDR_RESOLVED) {
         ERROR(errp, "result not equal to event_addr_resolved %s",
                 rdma_event_str(cm_event->event));
-        perror("rdma_resolve_addr");
+        error_report("rdma_resolve_addr");
         rdma_ack_cm_event(cm_event);
         ret = -EINVAL;
         goto err_resolve_get_addr;
@@ -2544,7 +2544,7 @@ static int qemu_rdma_connect(RDMAContext *rdma, Error **errp, bool return_path)
     }
 
     if (cm_event->event != RDMA_CM_EVENT_ESTABLISHED) {
-        perror("rdma_get_cm_event != EVENT_ESTABLISHED after rdma_connect");
+        error_report("rdma_get_cm_event != EVENT_ESTABLISHED after rdma_connect");
         ERROR(errp, "connecting to destination!");
         rdma_ack_cm_event(cm_event);
         goto err_rdma_source_connect;

tests/migration/guestperf/engine.py

@@ -113,7 +113,7 @@ class Engine(object):
         vcpus = src.command("query-cpus-fast")
         src_threads = []
         for vcpu in vcpus:
-            src_threads.append(vcpu["thread_id"])
+            src_threads.append(vcpu["thread-id"])
 
         # XXX how to get dst timings on remote host ?
 
@@ -153,7 +153,7 @@ class Engine(object):
                            max_bandwidth=scenario._bandwidth * 1024 * 1024)
 
         resp = src.command("migrate-set-parameters",
-                           downtime_limit=scenario._downtime / 1024.0)
+                           downtime_limit=scenario._downtime)
 
         if scenario._compression_mt:
             resp = src.command("migrate-set-capabilities",

tests/qtest/migration-test.c

@@ -27,6 +27,10 @@
 #include "migration-helpers.h"
 #include "tests/migration/migration-test.h"
 
+#if defined(__linux__)
+#include "linux/kvm.h"
+#endif
+
 /* TODO actually test the results and get rid of this */
 #define qtest_qmp_discard_response(...) qobject_unref(qtest_qmp(__VA_ARGS__))
 
@@ -467,6 +471,8 @@ typedef struct {
     bool use_shmem;
     /* only launch the target process */
     bool only_target;
+    /* Use dirty ring if true; dirty logging otherwise */
+    bool use_dirty_ring;
     char *opts_source;
     char *opts_target;
 } MigrateStart;
@@ -573,11 +579,13 @@ static int test_migrate_start(QTestState **from, QTestState **to,
         shmem_opts = g_strdup("");
     }
 
-    cmd_source = g_strdup_printf("-accel kvm -accel tcg%s%s "
+    cmd_source = g_strdup_printf("-accel kvm%s -accel tcg%s%s "
                                  "-name source,debug-threads=on "
                                  "-m %s "
                                  "-serial file:%s/src_serial "
                                  "%s %s %s %s",
+                                 args->use_dirty_ring ?
+                                 ",dirty-ring-size=4096" : "",
                                  machine_opts ? " -machine " : "",
                                  machine_opts ? machine_opts : "",
                                  memory_size, tmpfs,
@@ -587,12 +595,14 @@ static int test_migrate_start(QTestState **from, QTestState **to,
         *from = qtest_init(cmd_source);
     }
 
-    cmd_target = g_strdup_printf("-accel kvm -accel tcg%s%s "
+    cmd_target = g_strdup_printf("-accel kvm%s -accel tcg%s%s "
                                  "-name target,debug-threads=on "
                                  "-m %s "
                                  "-serial file:%s/dest_serial "
                                  "-incoming %s "
                                  "%s %s %s %s",
+                                 args->use_dirty_ring ?
+                                 ",dirty-ring-size=4096" : "",
                                  machine_opts ? " -machine " : "",
                                  machine_opts ? machine_opts : "",
                                  memory_size, tmpfs, uri,
@@ -785,12 +795,14 @@ static void test_baddest(void)
     test_migrate_end(from, to, false);
 }
 
-static void test_precopy_unix(void)
+static void test_precopy_unix_common(bool dirty_ring)
 {
     g_autofree char *uri = g_strdup_printf("unix:%s/migsocket", tmpfs);
     MigrateStart *args = migrate_start_new();
     QTestState *from, *to;
 
+    args->use_dirty_ring = dirty_ring;
+
     if (test_migrate_start(&from, &to, uri, args)) {
         return;
     }
@@ -825,6 +837,18 @@ static void test_precopy_unix(void)
     test_migrate_end(from, to, true);
 }
 
+static void test_precopy_unix(void)
+{
+    /* Using default dirty logging */
+    test_precopy_unix_common(false);
+}
+
+static void test_precopy_unix_dirty_ring(void)
+{
+    /* Using dirty ring tracking */
+    test_precopy_unix_common(true);
+}
+
 #if 0
 /* Currently upset on aarch64 TCG */
 static void test_ignore_shared(void)
@@ -1369,6 +1393,29 @@ static void test_multifd_tcp_cancel(void)
     test_migrate_end(from, to2, true);
 }
 
+static bool kvm_dirty_ring_supported(void)
+{
+#if defined(__linux__)
+    int ret, kvm_fd = open("/dev/kvm", O_RDONLY);
+
+    if (kvm_fd < 0) {
+        return false;
+    }
+
+    ret = ioctl(kvm_fd, KVM_CHECK_EXTENSION, KVM_CAP_DIRTY_LOG_RING);
+    close(kvm_fd);
+
+    /* We test with 4096 slots */
+    if (ret < 4096) {
+        return false;
+    }
+
+    return true;
+#else
+    return false;
+#endif
+}
+
 int main(int argc, char **argv)
 {
     char template[] = "/tmp/migration-test-XXXXXX";
@@ -1439,6 +1486,11 @@ int main(int argc, char **argv)
     qtest_add_func("/migration/multifd/tcp/zstd", test_multifd_tcp_zstd);
 #endif
 
+    if (kvm_dirty_ring_supported()) {
+        qtest_add_func("/migration/dirty_ring",
+                       test_precopy_unix_dirty_ring);
+    }
+
     ret = g_test_run();
 
     g_assert_cmpint(ret, ==, 0);

tools/virtiofsd/fuse_common.h

@@ -372,6 +372,11 @@ struct fuse_file_info {
  */
 #define FUSE_CAP_HANDLE_KILLPRIV_V2 (1 << 28)
 
+/**
+ * Indicates that file server supports extended struct fuse_setxattr_in
+ */
+#define FUSE_CAP_SETXATTR_EXT (1 << 29)
+
 /**
  * Ioctl flags
  *

tools/virtiofsd/fuse_lowlevel.c

@@ -1084,6 +1084,12 @@ static void do_open(fuse_req_t req, fuse_ino_t nodeid,
         return;
     }
 
+    /* File creation is handled by do_create() or do_mknod() */
+    if (arg->flags & (O_CREAT | O_TMPFILE)) {
+        fuse_reply_err(req, EINVAL);
+        return;
+    }
+
     memset(&fi, 0, sizeof(fi));
     fi.flags = arg->flags;
     fi.kill_priv = arg->open_flags & FUSE_OPEN_KILL_SUIDGID;
@@ -1419,8 +1425,13 @@ static void do_setxattr(fuse_req_t req, fuse_ino_t nodeid,
     struct fuse_setxattr_in *arg;
     const char *name;
     const char *value;
+    bool setxattr_ext = req->se->conn.want & FUSE_CAP_SETXATTR_EXT;
 
-    arg = fuse_mbuf_iter_advance(iter, sizeof(*arg));
+    if (setxattr_ext) {
+        arg = fuse_mbuf_iter_advance(iter, sizeof(*arg));
+    } else {
+        arg = fuse_mbuf_iter_advance(iter, FUSE_COMPAT_SETXATTR_IN_SIZE);
+    }
     name = fuse_mbuf_iter_advance_str(iter);
     if (!arg || !name) {
         fuse_reply_err(req, EINVAL);
@@ -1434,7 +1445,9 @@ static void do_setxattr(fuse_req_t req, fuse_ino_t nodeid,
     }
 
     if (req->se->op.setxattr) {
-        req->se->op.setxattr(req, nodeid, name, value, arg->size, arg->flags);
+        uint32_t setxattr_flags = setxattr_ext ? arg->setxattr_flags : 0;
+        req->se->op.setxattr(req, nodeid, name, value, arg->size, arg->flags,
+                             setxattr_flags);
     } else {
         fuse_reply_err(req, ENOSYS);
     }
@@ -1981,6 +1994,9 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid,
     if (arg->flags & FUSE_HANDLE_KILLPRIV_V2) {
         se->conn.capable |= FUSE_CAP_HANDLE_KILLPRIV_V2;
     }
+    if (arg->flags & FUSE_SETXATTR_EXT) {
+        se->conn.capable |= FUSE_CAP_SETXATTR_EXT;
+    }
 #ifdef HAVE_SPLICE
 #ifdef HAVE_VMSPLICE
     se->conn.capable |= FUSE_CAP_SPLICE_WRITE | FUSE_CAP_SPLICE_MOVE;
@@ -2116,6 +2132,10 @@ static void do_init(fuse_req_t req, fuse_ino_t nodeid,
         outarg.flags |= FUSE_HANDLE_KILLPRIV_V2;
     }
 
+    if (se->conn.want & FUSE_CAP_SETXATTR_EXT) {
+        outarg.flags |= FUSE_SETXATTR_EXT;
+    }
+
     fuse_log(FUSE_LOG_DEBUG, "   INIT: %u.%u\n", outarg.major, outarg.minor);
     fuse_log(FUSE_LOG_DEBUG, "   flags=0x%08x\n", outarg.flags);
     fuse_log(FUSE_LOG_DEBUG, "   max_readahead=0x%08x\n", outarg.max_readahead);

tools/virtiofsd/fuse_lowlevel.h

@@ -798,7 +798,8 @@ struct fuse_lowlevel_ops {
      *   fuse_reply_err
      */
     void (*setxattr)(fuse_req_t req, fuse_ino_t ino, const char *name,
-                     const char *value, size_t size, int flags);
+                     const char *value, size_t size, int flags,
+                     uint32_t setxattr_flags);
 
     /**
      * Get an extended attribute

tools/virtiofsd/helper.c

@@ -186,6 +186,7 @@ void fuse_cmdline_help(void)
            "                               to virtiofsd from guest applications.\n"
            "                               default: no_allow_direct_io\n"
            "    -o announce_submounts      Announce sub-mount points to the guest\n"
+           "    -o posix_acl/no_posix_acl  Enable/Disable posix_acl. (default: disabled)\n"
            );
 }
 

tools/virtiofsd/passthrough_ll.c

@@ -122,6 +122,7 @@ struct lo_inode {
 struct lo_cred {
     uid_t euid;
     gid_t egid;
+    mode_t umask;
 };
 
 enum {
@@ -172,6 +173,9 @@ struct lo_data {
     /* An O_PATH file descriptor to /proc/self/fd/ */
     int proc_self_fd;
     int user_killpriv_v2, killpriv_v2;
+    /* If set, virtiofsd is responsible for setting umask during creation */
+    bool change_umask;
+    int user_posix_acl, posix_acl;
 };
 
 static const struct fuse_opt lo_opts[] = {
@@ -204,6 +208,8 @@ static const struct fuse_opt lo_opts[] = {
     { "announce_submounts", offsetof(struct lo_data, announce_submounts), 1 },
     { "killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 1 },
     { "no_killpriv_v2", offsetof(struct lo_data, user_killpriv_v2), 0 },
+    { "posix_acl", offsetof(struct lo_data, user_posix_acl), 1 },
+    { "no_posix_acl", offsetof(struct lo_data, user_posix_acl), 0 },
     FUSE_OPT_END
 };
 static bool use_syslog = false;
@@ -702,6 +708,32 @@ static void lo_init(void *userdata, struct fuse_conn_info *conn)
         conn->want &= ~FUSE_CAP_HANDLE_KILLPRIV_V2;
         lo->killpriv_v2 = 0;
     }
+
+    if (lo->user_posix_acl == 1) {
+        /*
+         * User explicitly asked for this option. Enable it unconditionally.
+         * If connection does not have this capability, print error message
+         * now. It will fail later in fuse_lowlevel.c
+         */
+        if (!(conn->capable & FUSE_CAP_POSIX_ACL) ||
+            !(conn->capable & FUSE_CAP_DONT_MASK) ||
+            !(conn->capable & FUSE_CAP_SETXATTR_EXT)) {
+            fuse_log(FUSE_LOG_ERR, "lo_init: Can not enable posix acl."
+                     " kernel does not support FUSE_POSIX_ACL, FUSE_DONT_MASK"
+                     " or FUSE_SETXATTR_EXT capability.\n");
+        } else {
+            fuse_log(FUSE_LOG_DEBUG, "lo_init: enabling posix acl\n");
+        }
+
+        conn->want |= FUSE_CAP_POSIX_ACL | FUSE_CAP_DONT_MASK |
+                      FUSE_CAP_SETXATTR_EXT;
+        lo->change_umask = true;
+        lo->posix_acl = true;
+    } else {
+        /* User either did not specify anything or wants it disabled */
+        fuse_log(FUSE_LOG_DEBUG, "lo_init: disabling posix_acl\n");
+        conn->want &= ~FUSE_CAP_POSIX_ACL;
+    }
 }
 
 static void lo_getattr(fuse_req_t req, fuse_ino_t ino,
@@ -1134,7 +1166,8 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name)
  * ownership of caller.
  * TODO: What about selinux context?
  */
-static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
+static int lo_change_cred(fuse_req_t req, struct lo_cred *old,
+                          bool change_umask)
 {
     int res;
 
@@ -1154,11 +1187,14 @@ static int lo_change_cred(fuse_req_t req, struct lo_cred *old)
         return errno_save;
     }
 
+    if (change_umask) {
+        old->umask = umask(req->ctx.umask);
+    }
     return 0;
 }
 
 /* Regain Privileges */
-static void lo_restore_cred(struct lo_cred *old)
+static void lo_restore_cred(struct lo_cred *old, bool restore_umask)
 {
     int res;
 
@@ -1173,6 +1209,54 @@ static void lo_restore_cred(struct lo_cred *old)
         fuse_log(FUSE_LOG_ERR, "setegid(%u): %m\n", old->egid);
         exit(1);
     }
+
+    if (restore_umask)
+        umask(old->umask);
+}
+
+/*
+ * A helper to change cred and drop capability. Returns 0 on success and
+ * errno on error
+ */
+static int lo_drop_cap_change_cred(fuse_req_t req, struct lo_cred *old,
+                                   bool change_umask, const char *cap_name,
+                                   bool *cap_dropped)
+{
+    int ret;
+    bool __cap_dropped;
+
+    assert(cap_name);
+
+    ret = drop_effective_cap(cap_name, &__cap_dropped);
+    if (ret) {
+        return ret;
+    }
+
+    ret = lo_change_cred(req, old, change_umask);
+    if (ret) {
+        if (__cap_dropped) {
+            if (gain_effective_cap(cap_name)) {
+                fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_%s\n", cap_name);
+            }
+        }
+    }
+
+    if (cap_dropped) {
+        *cap_dropped = __cap_dropped;
+    }
+    return ret;
+}
+
+static void lo_restore_cred_gain_cap(struct lo_cred *old, bool restore_umask,
+                                     const char *cap_name)
+{
+    assert(cap_name);
+
+    lo_restore_cred(old, restore_umask);
+
+    if (gain_effective_cap(cap_name)) {
+        fuse_log(FUSE_LOG_ERR, "Failed to gain CAP_%s\n", cap_name);
+    }
 }
 
 static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
@@ -1202,7 +1286,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
         return;
     }
 
-    saverr = lo_change_cred(req, &old);
+    saverr = lo_change_cred(req, &old, lo->change_umask && !S_ISLNK(mode));
     if (saverr) {
         goto out;
     }
@@ -1211,7 +1295,7 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent,
 
     saverr = errno;
 
-    lo_restore_cred(&old);
+    lo_restore_cred(&old, lo->change_umask && !S_ISLNK(mode));
 
     if (res == -1) {
         goto out;
@@ -1917,7 +2001,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
         return;
     }
 
-    err = lo_change_cred(req, &old);
+    err = lo_change_cred(req, &old, lo->change_umask);
     if (err) {
         goto out;
     }
@@ -1928,7 +2012,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
     fd = openat(parent_inode->fd, name, fi->flags | O_CREAT | O_EXCL, mode);
     err = fd == -1 ? errno : 0;
 
-    lo_restore_cred(&old);
+    lo_restore_cred(&old, lo->change_umask);
 
     /* Ignore the error if file exists and O_EXCL was not given */
     if (err && (err != EEXIST || (fi->flags & O_EXCL))) {
@@ -2727,6 +2811,63 @@ static int xattr_map_server(const struct lo_data *lo, const char *server_name,
         assert(fchdir_res == 0);                       \
     } while (0)
 
+static bool block_xattr(struct lo_data *lo, const char *name)
+{
+    /*
+     * If user explicitly enabled posix_acl or did not provide any option,
+     * do not block acl. Otherwise block system.posix_acl_access and
+     * system.posix_acl_default xattrs.
+     */
+    if (lo->user_posix_acl) {
+        return false;
+    }
+    if (!strcmp(name, "system.posix_acl_access") ||
+        !strcmp(name, "system.posix_acl_default"))
+            return true;
+
+    return false;
+}
+
+/*
+ * Returns number of bytes in xattr_list after filtering on success. This
+ * could be zero as well if nothing is left after filtering.
+ *
+ * Returns negative error code on failure.
+ * xattr_list is modified in place.
+ */
+static int remove_blocked_xattrs(struct lo_data *lo, char *xattr_list,
+                                 unsigned in_size)
+{
+    size_t out_index, in_index;
+
+    /*
+     * As of now we only filter out acl xattrs. If acls are enabled or
+     * they have not been explicitly disabled, there is nothing to
+     * filter.
+     */
+    if (lo->user_posix_acl) {
+        return in_size;
+    }
+
+    out_index = 0;
+    in_index = 0;
+    while (in_index < in_size) {
+        char *in_ptr = xattr_list + in_index;
+
+        /* Length of current attribute name */
+        size_t in_len = strlen(xattr_list + in_index) + 1;
+
+        if (!block_xattr(lo, in_ptr)) {
+            if (in_index != out_index) {
+                memmove(xattr_list + out_index, xattr_list + in_index, in_len);
+            }
+            out_index += in_len;
+        }
+        in_index += in_len;
+     }
+    return out_index;
+}
+
 static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
                         size_t size)
 {
@@ -2740,6 +2881,11 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
     int saverr;
     int fd = -1;
 
+    if (block_xattr(lo, in_name)) {
+        fuse_reply_err(req, EOPNOTSUPP);
+        return;
+    }
+
     mapped_name = NULL;
     name = in_name;
     if (lo->xattrmap) {
@@ -2791,15 +2937,17 @@ static void lo_getxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
             goto out_err;
         }
         ret = fgetxattr(fd, name, value, size);
+        saverr = ret == -1 ? errno : 0;
     } else {
         /* fchdir should not fail here */
         FCHDIR_NOFAIL(lo->proc_self_fd);
         ret = getxattr(procname, name, value, size);
+        saverr = ret == -1 ? errno : 0;
         FCHDIR_NOFAIL(lo->root.fd);
     }
 
     if (ret == -1) {
-        goto out_err;
+        goto out;
     }
     if (size) {
         saverr = 0;
@@ -2864,15 +3012,17 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
             goto out_err;
         }
         ret = flistxattr(fd, value, size);
+        saverr = ret == -1 ? errno : 0;
     } else {
         /* fchdir should not fail here */
         FCHDIR_NOFAIL(lo->proc_self_fd);
         ret = listxattr(procname, value, size);
+        saverr = ret == -1 ? errno : 0;
         FCHDIR_NOFAIL(lo->root.fd);
     }
 
     if (ret == -1) {
-        goto out_err;
+        goto out;
     }
     if (size) {
         saverr = 0;
@@ -2926,6 +3076,12 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size)
                 goto out;
             }
         }
+
+        ret = remove_blocked_xattrs(lo, value, ret);
+        if (ret <= 0) {
+            saverr = -ret;
+            goto out;
+        }
         fuse_reply_buf(req, value, ret);
     } else {
         /*
@@ -2951,7 +3107,8 @@ out:
 }
 
 static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
-                        const char *value, size_t size, int flags)
+                        const char *value, size_t size, int flags,
+                        uint32_t extra_flags)
 {
     char procname[64];
     const char *name;
@@ -2961,6 +3118,14 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
     ssize_t ret;
     int saverr;
     int fd = -1;
+    bool switched_creds = false;
+    bool cap_fsetid_dropped = false;
+    struct lo_cred old = {};
+
+    if (block_xattr(lo, in_name)) {
+        fuse_reply_err(req, EOPNOTSUPP);
+        return;
+    }
 
     mapped_name = NULL;
     name = in_name;
@@ -2991,6 +3156,26 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
              ", name=%s value=%s size=%zd)\n", ino, name, value, size);
 
     sprintf(procname, "%i", inode->fd);
+    /*
+     * If we are setting posix access acl and if SGID needs to be
+     * cleared, then switch to caller's gid and drop CAP_FSETID
+     * and that should make sure host kernel clears SGID.
+     *
+     * This probably will not work when we support idmapped mounts.
+     * In that case we will need to find a non-root gid and switch
+     * to it. (Instead of gid in request). Fix it when we support
+     * idmapped mounts.
+     */
+    if (lo->posix_acl && !strcmp(name, "system.posix_acl_access")
+        && (extra_flags & FUSE_SETXATTR_ACL_KILL_SGID)) {
+        ret = lo_drop_cap_change_cred(req, &old, false, "FSETID",
+                                      &cap_fsetid_dropped);
+        if (ret) {
+            saverr = ret;
+            goto out;
+        }
+        switched_creds = true;
+    }
     if (S_ISREG(inode->filetype) || S_ISDIR(inode->filetype)) {
         fd = openat(lo->proc_self_fd, procname, O_RDONLY);
         if (fd < 0) {
@@ -2998,14 +3183,20 @@ static void lo_setxattr(fuse_req_t req, fuse_ino_t ino, const char *in_name,
             goto out;
         }
         ret = fsetxattr(fd, name, value, size, flags);
+        saverr = ret == -1 ? errno : 0;
     } else {
         /* fchdir should not fail here */
         FCHDIR_NOFAIL(lo->proc_self_fd);
         ret = setxattr(procname, name, value, size, flags);
+        saverr = ret == -1 ? errno : 0;
         FCHDIR_NOFAIL(lo->root.fd);
     }
-
+    if (switched_creds) {
-    saverr = ret == -1 ? errno : 0;
+        if (cap_fsetid_dropped)
+            lo_restore_cred_gain_cap(&old, false, "FSETID");
+        else
+            lo_restore_cred(&old, false);
+    }
 
 out:
     if (fd >= 0) {
@@ -3028,6 +3219,11 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name)
     int saverr;
     int fd = -1;
 
+    if (block_xattr(lo, in_name)) {
+        fuse_reply_err(req, EOPNOTSUPP);
+        return;
+    }
+
     mapped_name = NULL;
     name = in_name;
     if (lo->xattrmap) {
@@ -3064,15 +3260,15 @@ static void lo_removexattr(fuse_req_t req, fuse_ino_t ino, const char *in_name)
             goto out;
         }
         ret = fremovexattr(fd, name);
+        saverr = ret == -1 ? errno : 0;
     } else {
         /* fchdir should not fail here */
         FCHDIR_NOFAIL(lo->proc_self_fd);
         ret = removexattr(procname, name);
+        saverr = ret == -1 ? errno : 0;
         FCHDIR_NOFAIL(lo->root.fd);
     }
 
-    saverr = ret == -1 ? errno : 0;
-
 out:
     if (fd >= 0) {
         close(fd);
@@ -3559,10 +3755,6 @@ static void setup_nofile_rlimit(unsigned long rlimit_nofile)
 static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)
 {
     g_autofree char *localfmt = NULL;
-    struct timespec ts;
-    struct tm tm;
-    char sec_fmt[sizeof "2020-12-07 18:17:54"];
-    char zone_fmt[sizeof "+0100"];
 
     if (current_log_level < level) {
         return;
@@ -3574,23 +3766,10 @@ static void log_func(enum fuse_log_level level, const char *fmt, va_list ap)
             localfmt = g_strdup_printf("[ID: %08ld] %s", syscall(__NR_gettid),
                                        fmt);
         } else {
-            /* try formatting a broken-down timestamp */
+            g_autoptr(GDateTime) now = g_date_time_new_now_utc();
-            if (clock_gettime(CLOCK_REALTIME, &ts) != -1 &&
+            g_autofree char *nowstr = g_date_time_format(now, "%Y-%m-%d %H:%M:%S.%f%z");
-                localtime_r(&ts.tv_sec, &tm) != NULL &&
+            localfmt = g_strdup_printf("[%s] [ID: %08ld] %s",
-                strftime(sec_fmt, sizeof sec_fmt, "%Y-%m-%d %H:%M:%S",
+                                       nowstr, syscall(__NR_gettid), fmt);
-                         &tm) != 0 &&
-                strftime(zone_fmt, sizeof zone_fmt, "%z", &tm) != 0) {
-                localfmt = g_strdup_printf("[%s.%02ld%s] [ID: %08ld] %s",
-                                           sec_fmt,
-                                           ts.tv_nsec / (10L * 1000 * 1000),
-                                           zone_fmt, syscall(__NR_gettid),
-                                           fmt);
-            } else {
-                /* fall back to a flat timestamp */
-                localfmt = g_strdup_printf("[%" PRId64 "] [ID: %08ld] %s",
-                                           get_clock(), syscall(__NR_gettid),
-                                           fmt);
-            }
         }
         fmt = localfmt;
     }
@@ -3722,6 +3901,7 @@ int main(int argc, char *argv[])
         .allow_direct_io = 0,
         .proc_self_fd = -1,
         .user_killpriv_v2 = -1,
+        .user_posix_acl = -1,
     };
     struct lo_map_elem *root_elem;
     struct lo_map_elem *reserve_elem;
@@ -3850,6 +4030,12 @@ int main(int argc, char *argv[])
         exit(1);
     }
 
+    if (lo.user_posix_acl == 1 && !lo.xattr) {
+        fuse_log(FUSE_LOG_ERR, "Can't enable posix ACLs. xattrs are disabled."
+                 "\n");
+        exit(1);
+    }
+
     lo.use_statx = true;
 
     se = fuse_session_new(&args, &lo_oper, sizeof(lo_oper), &lo);

tools/virtiofsd/passthrough_seccomp.c

@@ -114,6 +114,7 @@ static const int syscall_allowlist[] = {
     SCMP_SYS(utimensat),
     SCMP_SYS(write),
     SCMP_SYS(writev),
+    SCMP_SYS(umask),
 };
 
 /* Syscalls used when --syslog is enabled */