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From 781a055c17400e953bb7929434fe7a2e6517d5e8 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Thu, 17 Jan 2019 18:31:59 +0100
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Subject: [PATCH] sd-bus: use "queue" message references for managing r/w
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 message queues in connection objects
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Let's make use of the new concept the previous commit added.
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See: #4846
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(cherry picked from commit c1757a70eac0382c4837a3833d683919f6a48ed7)
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Related: CVE-2020-1712
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---
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 src/libsystemd/sd-bus/bus-socket.c |  6 ++-
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 src/libsystemd/sd-bus/sd-bus.c     | 60 ++++++++++++++----------------
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 2 files changed, 32 insertions(+), 34 deletions(-)
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diff --git a/src/libsystemd/sd-bus/bus-socket.c b/src/libsystemd/sd-bus/bus-socket.c
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index 17cfa8e1fd..4a72795d2b 100644
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--- a/src/libsystemd/sd-bus/bus-socket.c
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+++ b/src/libsystemd/sd-bus/bus-socket.c
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@@ -1116,8 +1116,10 @@ static int bus_socket_make_message(sd_bus *bus, size_t size) {
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         bus->fds = NULL;
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         bus->n_fds = 0;
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-        if (t)
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-                bus->rqueue[bus->rqueue_size++] = t;
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+        if (t) {
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+                bus->rqueue[bus->rqueue_size++] = bus_message_ref_queued(t, bus);
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+                sd_bus_message_unref(t);
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+        }
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         return 1;
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 }
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diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
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index 68ad6cbe89..a3509f7e89 100644
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--- a/src/libsystemd/sd-bus/sd-bus.c
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+++ b/src/libsystemd/sd-bus/sd-bus.c
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@@ -148,13 +148,13 @@ static void bus_reset_queues(sd_bus *b) {
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         assert(b);
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         while (b->rqueue_size > 0)
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-                sd_bus_message_unref(b->rqueue[--b->rqueue_size]);
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+                bus_message_unref_queued(b->rqueue[--b->rqueue_size], b);
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         b->rqueue = mfree(b->rqueue);
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         b->rqueue_allocated = 0;
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         while (b->wqueue_size > 0)
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-                sd_bus_message_unref(b->wqueue[--b->wqueue_size]);
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+                bus_message_unref_queued(b->wqueue[--b->wqueue_size], b);
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         b->wqueue = mfree(b->wqueue);
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         b->wqueue_allocated = 0;
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@@ -493,7 +493,7 @@ static int synthesize_connected_signal(sd_bus *bus) {
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         /* Insert at the very front */
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         memmove(bus->rqueue + 1, bus->rqueue, sizeof(sd_bus_message*) * bus->rqueue_size);
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-        bus->rqueue[0] = TAKE_PTR(m);
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+        bus->rqueue[0] = bus_message_ref_queued(m, bus);
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         bus->rqueue_size++;
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         return 0;
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@@ -1760,7 +1760,7 @@ static int dispatch_wqueue(sd_bus *bus) {
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                          * anyway. */
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                         bus->wqueue_size--;
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-                        sd_bus_message_unref(bus->wqueue[0]);
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+                        bus_message_unref_queued(bus->wqueue[0], bus);
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                         memmove(bus->wqueue, bus->wqueue + 1, sizeof(sd_bus_message*) * bus->wqueue_size);
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                         bus->windex = 0;
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@@ -1789,6 +1789,15 @@ int bus_rqueue_make_room(sd_bus *bus) {
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         return 0;
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 }
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+static void rqueue_drop_one(sd_bus *bus, size_t i) {
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+        assert(bus);
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+        assert(i < bus->rqueue_size);
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+
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+        bus_message_unref_queued(bus->rqueue[i], bus);
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+        memmove(bus->rqueue + i, bus->rqueue + i + 1, sizeof(sd_bus_message*) * (bus->rqueue_size - i - 1));
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+        bus->rqueue_size--;
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+}
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+
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 static int dispatch_rqueue(sd_bus *bus, bool hint_priority, int64_t priority, sd_bus_message **m) {
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         int r, ret = 0;
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@@ -1803,10 +1812,8 @@ static int dispatch_rqueue(sd_bus *bus, bool hint_priority, int64_t priority, sd
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         for (;;) {
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                 if (bus->rqueue_size > 0) {
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                         /* Dispatch a queued message */
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-
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-                        *m = bus->rqueue[0];
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-                        bus->rqueue_size--;
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-                        memmove(bus->rqueue, bus->rqueue + 1, sizeof(sd_bus_message*) * bus->rqueue_size);
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+                        *m = sd_bus_message_ref(bus->rqueue[0]);
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+                        rqueue_drop_one(bus, 0);
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                         return 1;
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                 }
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@@ -1884,7 +1891,7 @@ _public_ int sd_bus_send(sd_bus *bus, sd_bus_message *_m, uint64_t *cookie) {
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                          * of the wqueue array is always allocated so
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                          * that we always can remember how much was
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                          * written. */
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-                        bus->wqueue[0] = sd_bus_message_ref(m);
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+                        bus->wqueue[0] = bus_message_ref_queued(m, bus);
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                         bus->wqueue_size = 1;
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                         bus->windex = idx;
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                 }
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@@ -1898,7 +1905,7 @@ _public_ int sd_bus_send(sd_bus *bus, sd_bus_message *_m, uint64_t *cookie) {
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                 if (!GREEDY_REALLOC(bus->wqueue, bus->wqueue_allocated, bus->wqueue_size + 1))
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                         return -ENOMEM;
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-                bus->wqueue[bus->wqueue_size++] = sd_bus_message_ref(m);
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+                bus->wqueue[bus->wqueue_size++] = bus_message_ref_queued(m, bus);
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         }
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 finish:
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@@ -2124,37 +2131,30 @@ _public_ int sd_bus_call(
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                 usec_t left;
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                 while (i < bus->rqueue_size) {
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-                        sd_bus_message *incoming = NULL;
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+                        _cleanup_(sd_bus_message_unrefp) sd_bus_message *incoming = NULL;
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-                        incoming = bus->rqueue[i];
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+                        incoming = sd_bus_message_ref(bus->rqueue[i]);
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                         if (incoming->reply_cookie == cookie) {
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                                 /* Found a match! */
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-                                memmove(bus->rqueue + i, bus->rqueue + i + 1, sizeof(sd_bus_message*) * (bus->rqueue_size - i - 1));
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-                                bus->rqueue_size--;
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+                                rqueue_drop_one(bus, i);
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                                 log_debug_bus_message(incoming);
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                                 if (incoming->header->type == SD_BUS_MESSAGE_METHOD_RETURN) {
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                                         if (incoming->n_fds <= 0 || bus->accept_fd) {
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                                                 if (reply)
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-                                                        *reply = incoming;
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-                                                else
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-                                                        sd_bus_message_unref(incoming);
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+                                                        *reply = TAKE_PTR(incoming);
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                                                 return 1;
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                                         }
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-                                        r = sd_bus_error_setf(error, SD_BUS_ERROR_INCONSISTENT_MESSAGE, "Reply message contained file descriptors which I couldn't accept. Sorry.");
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-                                        sd_bus_message_unref(incoming);
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-                                        return r;
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+                                        return sd_bus_error_setf(error, SD_BUS_ERROR_INCONSISTENT_MESSAGE, "Reply message contained file descriptors which I couldn't accept. Sorry.");
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-                                } else if (incoming->header->type == SD_BUS_MESSAGE_METHOD_ERROR) {
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-                                        r = sd_bus_error_copy(error, &incoming->error);
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-                                        sd_bus_message_unref(incoming);
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-                                        return r;
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-                                } else {
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+                                } else if (incoming->header->type == SD_BUS_MESSAGE_METHOD_ERROR)
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+                                        return sd_bus_error_copy(error, &incoming->error);
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+                                else {
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                                         r = -EIO;
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                                         goto fail;
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                                 }
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@@ -2164,15 +2164,11 @@ _public_ int sd_bus_call(
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                                    incoming->sender &&
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                                    streq(bus->unique_name, incoming->sender)) {
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-                                memmove(bus->rqueue + i, bus->rqueue + i + 1, sizeof(sd_bus_message*) * (bus->rqueue_size - i - 1));
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-                                bus->rqueue_size--;
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+                                rqueue_drop_one(bus, i);
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-                                /* Our own message? Somebody is trying
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-                                 * to send its own client a message,
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-                                 * let's not dead-lock, let's fail
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-                                 * immediately. */
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+                                /* Our own message? Somebody is trying to send its own client a message,
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+                                 * let's not dead-lock, let's fail immediately. */
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-                                sd_bus_message_unref(incoming);
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                                 r = -ELOOP;
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                                 goto fail;
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                         }