[pulseaudio-discuss] [PATCH] alsa-card: fix null dereference

Tanu Kaskinen tanuk at iki.fi
Thu May 24 17:31:51 UTC 2018

jack->melem can be null if the jack disappears between probing the card
and the init_jacks() call. I don't know if jacks actually ever disappear
like that (seems unlikely), but this check is in any case needed as long
as init_jacks() has proper handling for the jack disappearing case
(rather than just an assert).

There was a crash report[1] that indicated that card_suspend_changed()
called report_jack_state() with a null melem. I don't know if that was
because the jack actually disappeared, or is there some other bug too.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=104385
 src/modules/alsa/module-alsa-card.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/modules/alsa/module-alsa-card.c b/src/modules/alsa/module-alsa-card.c
index b193d40cc..1f78f18d1 100644
--- a/src/modules/alsa/module-alsa-card.c
+++ b/src/modules/alsa/module-alsa-card.c
@@ -640,7 +640,8 @@ static pa_hook_result_t card_suspend_changed(pa_core *c, pa_card *card, struct u
     if (card->suspend_cause == 0) {
         /* We were unsuspended, update jack state in case it changed while we were suspended */
         PA_HASHMAP_FOREACH(jack, u->jacks, state) {
-            report_jack_state(jack->melem, 0);
+            if (jack->melem)
+                report_jack_state(jack->melem, 0);

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