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From 980418c331293aeb8595fcc95cbc4a9e1a485eda Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 25 Feb 2019 11:02:46 +0100
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Subject: [PATCH] sd-bus: deal with cookie overruns
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Apparently this happens IRL. Let's carefully deal with issues like this:
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when we overrun, let's not go back to zero but instead leave the highest
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cookie bit set. We use that as indication that we are in "overrun
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territory", and then are particularly careful with checking cookies,
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i.e. that they haven't been used for still outstanding replies yet. This
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should retain the quick cookie generation behaviour we used to have, but
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permits dealing with overruns.
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Replaces: #11804
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Fixes: #11809
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(cherry picked from commit 1f82f5bb4237ed5f015daf93f818e9db95e764b8)
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Resolves: #1694999
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---
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src/libsystemd/sd-bus/sd-bus.c | 47 +++++++++++++++++++++++++++++++++-
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1 file changed, 46 insertions(+), 1 deletion(-)
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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 f53a98d6bf..3583e24e64 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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@@ -1597,6 +1597,47 @@ _public_ int sd_bus_get_bus_id(sd_bus *bus, sd_id128_t *id) {
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return 0;
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}
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+#define COOKIE_CYCLED (UINT32_C(1) << 31)
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+
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+static uint64_t cookie_inc(uint64_t cookie) {
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+
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+ /* Stay within the 32bit range, since classic D-Bus can't deal with more */
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+ if (cookie >= UINT32_MAX)
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+ return COOKIE_CYCLED; /* Don't go back to zero, but use the highest bit for checking
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+ * whether we are looping. */
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+
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+ return cookie + 1;
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+}
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+
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+static int next_cookie(sd_bus *b) {
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+ uint64_t new_cookie;
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+
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+ assert(b);
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+
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+ new_cookie = cookie_inc(b->cookie);
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+
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+ /* Small optimization: don't bother with checking for cookie reuse until we overran cookiespace at
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+ * least once, but then do it thorougly. */
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+ if (FLAGS_SET(new_cookie, COOKIE_CYCLED)) {
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+ uint32_t i;
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+
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+ /* Check if the cookie is currently in use. If so, pick the next one */
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+ for (i = 0; i < COOKIE_CYCLED; i++) {
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+ if (!ordered_hashmap_contains(b->reply_callbacks, &new_cookie))
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+ goto good;
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+
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+ new_cookie = cookie_inc(new_cookie);
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+ }
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+
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+ /* Can't fulfill request */
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+ return -EBUSY;
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+ }
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+
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+good:
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+ b->cookie = new_cookie;
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+ return 0;
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+}
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+
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static int bus_seal_message(sd_bus *b, sd_bus_message *m, usec_t timeout) {
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int r;
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@@ -1620,7 +1661,11 @@ static int bus_seal_message(sd_bus *b, sd_bus_message *m, usec_t timeout) {
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return r;
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}
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- return sd_bus_message_seal(m, ++b->cookie, timeout);
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+ r = next_cookie(b);
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+ if (r < 0)
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+ return r;
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+
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+ return sd_bus_message_seal(m, b->cookie, timeout);
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}
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static int bus_remarshal_message(sd_bus *b, sd_bus_message **m) {
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