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From 598eecf5c1c948535ca626833bc5cea59060913f Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Wed, 20 Apr 2022 22:30:22 +0200
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Subject: [PATCH] sd-bus: switch to a manual overflow check in
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sd_bus_track_add_name()
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This is generally used in a directly client controllable way, hence we
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should handle ref count overflow gracefully, instead of hitting an
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assert().
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As discussed:
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https://github.com/systemd/systemd/pull/23099#discussion_r854341850
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(cherry picked from commit 7f40cb7c86b0fff3a82096a9499570bad9c19fd2)
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[msekleta: We've never switched to using track_item_ref/unref introduced
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in c2d7dd35d2 hence we still had potential undefined behavior related to
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overflow check and this commit fixes that.]
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Related: #2047373
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---
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src/libsystemd/sd-bus/bus-track.c | 10 +++++++---
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1 file changed, 7 insertions(+), 3 deletions(-)
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diff --git a/src/libsystemd/sd-bus/bus-track.c b/src/libsystemd/sd-bus/bus-track.c
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index 8893f190a1..b818e93bec 100644
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--- a/src/libsystemd/sd-bus/bus-track.c
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+++ b/src/libsystemd/sd-bus/bus-track.c
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@@ -208,12 +208,16 @@ _public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
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i = hashmap_get(track->names, name);
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if (i) {
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if (track->recursive) {
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- unsigned k = i->n_ref + 1;
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+ assert(i->n_ref > 0);
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- if (k < i->n_ref) /* Check for overflow */
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+ /* Manual oveflow check (instead of a DEFINE_TRIVIAL_REF_FUNC() helper or so), so
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+ * that we can return a proper error, given this is almost always called in a
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+ * directly client controllable way, and thus better should never hit an assertion
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+ * here. */
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+ if (i->n_ref >= UINT_MAX)
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return -EOVERFLOW;
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- i->n_ref = k;
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+ i->n_ref++;
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}
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bus_track_remove_from_queue(track);
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