sd-bus: switch to a manual overflow check in sd_bus_track_add_name()

This is generally used in a directly client controllable way, hence we
should handle ref count overflow gracefully, instead of hitting an
assert().

As discussed:

https://github.com/systemd/systemd/pull/23099#discussion_r854341850

TODO

@@ -78,6 +78,10 @@ Janitorial Clean-ups:
 
 Features:
 
+* drop support for kernels that lack ambient capabilities support (i.e. make
+  4.3 new baseline). Then drop support for "!!" modifier for ExecStart= which
+  is only supported for such old kernels
+
 * sd-event: compat wd reuse in inotify code: keep a set of removed watch
   descriptors, and clear this set piecemeal when we see the IN_IGNORED event
   for it, or when read() returns EAGAIN or on IN_Q_OVERFLOW. Then, whenever we

man/systemd-creds.xml

@@ -163,6 +163,20 @@
         and thus decryption is entirely automatic.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><command>has-tpm2</command></term>
+
+        <listitem><para>Reports whether the system is equipped with a TPM2 device usable for protecting
+        credentials. If the a TPM2 device has been discovered, is supported, and is being used by firmware,
+        by the OS kernel drivers and by userspace (i.e. systemd) this prints <literal>yes</literal> and exits
+        with exit status zero. If no such device is discovered/supported/used, prints
+        <literal>no</literal>. Otherwise prints <literal>partial</literal>. In either of these two cases
+        exits with non-zero exit status. It also shows three lines indicating separately whether drivers,
+        firmware and the system discovered/support/use TPM2.</para>
+
+        <para>Combine with <option>--quiet</option> to suppress the output.</para></listitem>
+      </varlistentry>
+
       <xi:include href="standard-options.xml" xpointer="help" />
       <xi:include href="standard-options.xml" xpointer="version" />
     </variablelist>
@@ -314,6 +328,14 @@
         <citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><option>--quiet</option></term>
+        <term><option>-q</option></term>
+
+        <listitem><para>When used with <command>has-tpm2</command> suppresses the output, and only returns an
+        exit status indicating support for TPM2.</para></listitem>
+      </varlistentry>
+
       <xi:include href="standard-options.xml" xpointer="no-pager" />
       <xi:include href="standard-options.xml" xpointer="no-legend" />
       <xi:include href="standard-options.xml" xpointer="json" />
@@ -324,6 +346,12 @@
     <title>Exit status</title>
 
     <para>On success, 0 is returned.</para>
+
+    <para>In case of the <command>has-tpm2</command> command returns 0 if a TPM2 device is discovered,
+    supported and used by firmware, driver, and userspace (i.e. systemd). Otherwise returns the OR
+    combination of the value 1 (in case firmware support is missing), 2 (in case driver support is missing)
+    and 4 (in case userspace support is missing). If no TPM2 support is available at all, value 7 is hence
+    returned.</para>
   </refsect1>
 
   <refsect1>

src/basic/macro.h

@@ -399,7 +399,7 @@ static inline int __coverity_check_and_return__(int condition) {
                 /* For type check. */                           \
                 unsigned *q = &p->n_ref;                        \
                 assert(*q > 0);                                 \
-                assert(*q < UINT_MAX);                          \
+                assert_se(*q < UINT_MAX);                       \
                                                                 \
                 (*q)++;                                         \
                 return p;                                       \

src/boot/bootctl.c

@@ -47,6 +47,7 @@
 #include "terminal-util.h"
 #include "tmpfile-util.h"
 #include "tmpfile-util-label.h"
+#include "tpm2-util.h"
 #include "umask-util.h"
 #include "utf8.h"
 #include "util.h"
@@ -1697,10 +1698,10 @@ static int verb_status(int argc, char *argv[], void *userdata) {
                         { EFI_LOADER_FEATURE_RANDOM_SEED,             "Support for passing random seed to OS" },
                         { EFI_LOADER_FEATURE_LOAD_DRIVER,             "Load drop-in drivers"                  },
                 };
-
                 _cleanup_free_ char *fw_type = NULL, *fw_info = NULL, *loader = NULL, *loader_path = NULL, *stub = NULL;
                 sd_id128_t loader_part_uuid = SD_ID128_NULL;
                 uint64_t loader_features = 0;
+                Tpm2Support s;
                 int have;
 
                 read_efi_var(EFI_LOADER_VARIABLE(LoaderFirmwareType), &fw_type);
@@ -1723,7 +1724,15 @@ static int verb_status(int argc, char *argv[], void *userdata) {
                 printf("  Secure Boot: %sd (%s)\n",
                        enable_disable(IN_SET(secure, SECURE_BOOT_USER, SECURE_BOOT_DEPLOYED)),
                        secure_boot_mode_to_string(secure));
-                printf(" TPM2 Support: %s\n", yes_no(efi_has_tpm2()));
+
+                s = tpm2_support();
+                printf(" TPM2 Support: %s%s%s\n",
+                       FLAGS_SET(s, TPM2_SUPPORT_FIRMWARE|TPM2_SUPPORT_DRIVER) ? ansi_highlight_green() :
+                       (s & (TPM2_SUPPORT_FIRMWARE|TPM2_SUPPORT_DRIVER)) != 0 ? ansi_highlight_red() : ansi_highlight_yellow(),
+                       FLAGS_SET(s, TPM2_SUPPORT_FIRMWARE|TPM2_SUPPORT_DRIVER) ? "yes" :
+                       (s & TPM2_SUPPORT_FIRMWARE) ? "firmware only, driver unavailable" :
+                       (s & TPM2_SUPPORT_DRIVER) ? "driver only, firmware unavailable" : "no",
+                       ansi_normal());
 
                 k = efi_get_reboot_to_firmware();
                 if (k > 0)

src/creds/creds.c

@@ -48,6 +48,7 @@ static bool arg_name_any = false;
 static usec_t arg_timestamp = USEC_INFINITY;
 static usec_t arg_not_after = USEC_INFINITY;
 static bool arg_pretty = false;
+static bool arg_quiet = false;
 
 static const char* transcode_mode_table[_TRANSCODE_MAX] = {
         [TRANSCODE_OFF] = "off",
@@ -525,6 +526,34 @@ static int verb_setup(int argc, char **argv, void *userdata) {
         return EXIT_SUCCESS;
 }
 
+static int verb_has_tpm2(int argc, char **argv, void *userdata) {
+        Tpm2Support s;
+
+        s = tpm2_support();
+
+        if (!arg_quiet) {
+                if (s == TPM2_SUPPORT_FULL)
+                        puts("yes");
+                else if (s == TPM2_SUPPORT_NONE)
+                        puts("no");
+                else
+                        puts("partial");
+
+                printf("%sfirmware\n"
+                       "%sdriver\n"
+                       "%ssystem\n",
+                       plus_minus(s & TPM2_SUPPORT_FIRMWARE),
+                       plus_minus(s & TPM2_SUPPORT_DRIVER),
+                       plus_minus(s & TPM2_SUPPORT_SYSTEM));
+        }
+
+        /* Return inverted bit flags. So that TPM2_SUPPORT_FULL becomes EXIT_SUCCESS and the other values
+         * become some reasonable values 1…7. i.e. the flags we return here tell what is missing rather than
+         * what is there, acknowledging the fact that for process exit statusses it is customary to return
+         * zero (EXIT_FAILURE) when all is good, instead of all being bad. */
+        return ~s & TPM2_SUPPORT_FULL;
+}
+
 static int verb_help(int argc, char **argv, void *userdata) {
         _cleanup_free_ char *link = NULL;
         int r;
@@ -543,6 +572,7 @@ static int verb_help(int argc, char **argv, void *userdata) {
                "                          ciphertext credential file\n"
                "  decrypt INPUT [OUTPUT]  Decrypt ciphertext credential file and write to\n"
                "                          plaintext credential file\n"
+               "  has-tpm2                Report whether TPM2 support is available\n"
                "  -h --help               Show this help\n"
                "     --version            Show package version\n"
                "\n%3$sOptions:%4$s\n"
@@ -568,6 +598,7 @@ static int verb_help(int argc, char **argv, void *userdata) {
                "                          Pick TPM2 device\n"
                "     --tpm2-pcrs=PCR1+PCR2+PCR3+…\n"
                "                          Specify TPM2 PCRs to seal against\n"
+               "  -q --quiet              Suppress output for 'has-tpm2' verb\n"
                "\nSee the %2$s for details.\n"
                , program_invocation_short_name
                , link
@@ -612,6 +643,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "name",        required_argument, NULL, ARG_NAME        },
                 { "timestamp",   required_argument, NULL, ARG_TIMESTAMP   },
                 { "not-after",   required_argument, NULL, ARG_NOT_AFTER   },
+                { "quiet",       no_argument,       NULL, 'q'             },
                 {}
         };
 
@@ -620,7 +652,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "hHTp", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "hHTpq", options, NULL)) >= 0) {
 
                 switch (c) {
 
@@ -761,6 +793,10 @@ static int parse_argv(int argc, char *argv[]) {
 
                         break;
 
+                case 'q':
+                        arg_quiet = true;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -784,6 +820,7 @@ static int creds_main(int argc, char *argv[]) {
                 { "decrypt",  2,        3,        0,            verb_decrypt  },
                 { "setup",    VERB_ANY, 1,        0,            verb_setup    },
                 { "help",     VERB_ANY, 1,        0,            verb_help     },
+                { "has-tpm2", VERB_ANY, 1,        0,            verb_has_tpm2 },
                 {}
         };
 

src/libsystemd/sd-bus/bus-track.c

@@ -48,7 +48,7 @@ static struct track_item* track_item_free(struct track_item *i) {
         return mfree(i);
 }
 
-DEFINE_PRIVATE_TRIVIAL_REF_UNREF_FUNC(struct track_item, track_item, track_item_free);
+DEFINE_PRIVATE_TRIVIAL_UNREF_FUNC(struct track_item, track_item, track_item_free);
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct track_item*, track_item_unref);
 DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(track_item_hash_ops, char, string_hash_func, string_compare_func,
                                               struct track_item, track_item_free);
@@ -190,8 +190,18 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
 
         i = hashmap_get(track->names, name);
         if (i) {
-                if (track->recursive)
-                        track_item_ref(i);
+                if (track->recursive) {
+                        assert(i->n_ref > 0);
+
+                        /* Manual oveflow check (instead of a DEFINE_TRIVIAL_REF_FUNC() helper or so), so
+                         * that we can return a proper error, given this is almost always called in a
+                         * directly client controllable way, and thus better should never hit an assertion
+                         * here. */
+                        if (i->n_ref >= UINT_MAX)
+                                return -EOVERFLOW;
+
+                        i->n_ref++;
+                }
 
                 bus_track_remove_from_queue(track);
                 return 0;

src/shared/condition.c

@@ -50,6 +50,7 @@
 #include "string-table.h"
 #include "string-util.h"
 #include "tomoyo-util.h"
+#include "tpm2-util.h"
 #include "udev-util.h"
 #include "uid-alloc-range.h"
 #include "user-util.h"
@@ -623,29 +624,14 @@ static int condition_test_ac_power(Condition *c, char **env) {
 }
 
 static int has_tpm2(void) {
-        int r;
-
         /* Checks whether the system has at least one TPM2 resource manager device, i.e. at least one "tpmrm"
-         * class device */
+         * class device. Alternatively, we are also happy if the firmware reports support (this is to cover
+         * for cases where we simply haven't loaded the driver for it yet, i.e. during early boot where we
+         * very likely want to use this condition check).
+         *
+         * Note that we don't check if we ourselves are built with TPM2 support here! */
 
-        r = dir_is_empty("/sys/class/tpmrm");
-        if (r == 0)
-                return true; /* nice! we have a device */
-
-        /* Hmm, so Linux doesn't know of the TPM2 device (or we couldn't check for it), most likely because
-         * the driver wasn't loaded yet. Let's see if the firmware knows about a TPM2 device, in this
-         * case. This way we can answer the TPM2 question already during early boot (where we most likely
-         * need it) */
-        if (efi_has_tpm2())
-                return true;
-
-        /* OK, this didn't work either, in this case propagate the original errors */
-        if (r == -ENOENT)
-                return false;
-        if (r < 0)
-                return log_debug_errno(r, "Failed to determine whether system has TPM2 support: %m");
-
-        return !r;
+        return (tpm2_support() & (TPM2_SUPPORT_DRIVER|TPM2_SUPPORT_FIRMWARE)) != 0;
 }
 
 static int condition_test_security(Condition *c, char **env) {

src/shared/tpm2-util.c

@@ -1,7 +1,9 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include "efi-api.h"
 #include "extract-word.h"
 #include "parse-util.h"
+#include "stat-util.h"
 #include "tpm2-util.h"
 
 #if HAVE_TPM2
@@ -1453,3 +1455,24 @@ int tpm2_primary_alg_from_string(const char *alg) {
                 return TPM2_ALG_RSA;
         return -EINVAL;
 }
+
+Tpm2Support tpm2_support(void) {
+        Tpm2Support support = TPM2_SUPPORT_NONE;
+        int r;
+
+        r = dir_is_empty("/sys/class/tpmrm");
+        if (r < 0) {
+                if (r != -ENOENT)
+                        log_debug_errno(r, "Unable to test whether /sys/class/tpmrm/ exists and is populated, assuming it is not: %m");
+        } else if (r == 0) /* populated! */
+                support |= TPM2_SUPPORT_DRIVER;
+
+        if (efi_has_tpm2())
+                support |= TPM2_SUPPORT_FIRMWARE;
+
+#if HAVE_TPM2
+        support |= TPM2_SUPPORT_SYSTEM;
+#endif
+
+        return support;
+}

src/shared/tpm2-util.h

@@ -89,3 +89,15 @@ typedef struct {
         uint32_t search_pcr_mask;
         const char *device;
 } systemd_tpm2_plugin_params;
+
+typedef enum Tpm2Support {
+        /* NOTE! The systemd-creds tool returns these flags 1:1 as exit status. Hence these flags are pretty
+         * much ABI! Hence, be extra careful when changing/extending these definitions. */
+        TPM2_SUPPORT_NONE     = 0,       /* no support */
+        TPM2_SUPPORT_FIRMWARE = 1 << 0,  /* firmware reports TPM2 was used */
+        TPM2_SUPPORT_DRIVER   = 1 << 1,  /* the kernel has a driver loaded for it */
+        TPM2_SUPPORT_SYSTEM   = 1 << 2,  /* we support it ourselves */
+        TPM2_SUPPORT_FULL     = TPM2_SUPPORT_FIRMWARE|TPM2_SUPPORT_DRIVER|TPM2_SUPPORT_SYSTEM,
+} Tpm2Support;
+
+Tpm2Support tpm2_support(void);