From 779d08beeed45b765f3a696f209041d87bd9d5fd Mon Sep 17 00:00:00 2001 From: Lawrence Rust Date: Thu, 7 Jun 2012 11:52:29 +0200 Subject: [PATCH] libmyth: Prevent an access violation by the ALSA library In audiooutputalsa.cpp, AudioOutputALSA::GetALSADevices calls the ALSA API snd_device_name_hint with a card index of -1 to obtain a list of hints for all cards. Unfortunately, with libasound.so.2.0 this API can cause an access violation when the card index is -1. Running with valgrind shows that snd_device_name_hint makes reference to previously freed memory when the card index is -1. This patch enumerates the cards using other ALSA APIs, thus avoiding the SEGV. Signed-off-by: Lawrence Rust --- mythtv/libs/libmyth/audio/audiooutputalsa.cpp | 52 +++++++++++++++++-------- 1 files changed, 35 insertions(+), 17 deletions(-) diff --git a/mythtv/libs/libmyth/audio/audiooutputalsa.cpp b/mythtv/libs/libmyth/audio/audiooutputalsa.cpp index 176252a..5c6c202 100644 --- a/mythtv/libs/libmyth/audio/audiooutputalsa.cpp +++ b/mythtv/libs/libmyth/audio/audiooutputalsa.cpp @@ -1011,26 +1011,44 @@ bool AudioOutputALSA::OpenMixer(void) QMap *AudioOutputALSA::GetDevices(const char *type) { QMap *alsadevs = new QMap(); - void **hints, **n; - char *name, *desc; - if (snd_device_name_hint(-1, type, &hints) < 0) - return alsadevs; - n = hints; - - while (*n != NULL) + // Loop through the sound cards to get Alsa device hints. + // NB Don't use snd_device_name_hint(-1,..) since there is a potential + // access violation using this ALSA API with libasound.so.2.0.0. + // See http://code.google.com/p/chromium/issues/detail?id=95797 + int card = -1; + while (!snd_card_next(&card) && card >= 0) { - name = snd_device_name_get_hint(*n, "NAME"); - desc = snd_device_name_get_hint(*n, "DESC"); - if (name && desc && strcmp(name, "null")) - alsadevs->insert(name, desc); - if (name) - free(name); - if (desc) - free(desc); - n++; + void** hints = NULL; + int error = snd_device_name_hint(card, type, &hints); + if (error == 0) + { + void *hint; + for (int i = 0; (hint = hints[i]) != NULL; ++i) + { + char *name = snd_device_name_get_hint(hint, "NAME"); + if (name) + { + char *desc = snd_device_name_get_hint(hint, "DESC"); + if (desc) + { + if (strcmp(name, "null")) + alsadevs->insert(name, desc); + free(desc); + } + free(name); + } + } + + snd_device_name_free_hint(hints); + } + else + { + VBERROR(QString("Failed to get device hints for card %1, error %2") + .arg(card).arg(error)); + } } - snd_device_name_free_hint(hints); + // Work around ALSA bug < 1.0.22 ; where snd_device_name_hint can corrupt // global ALSA memory context #if SND_LIB_MAJOR == 1 -- 1.7.4.1