Ticket #10809: 0001-libmyth-Prevent-an-access-violation-by-the-ALSA-libr.2.patch

File 0001-libmyth-Prevent-an-access-violation-by-the-ALSA-libr.2.patch, 3.2 KB (added by Lawrence Rust <lvr@…>, 12 years ago)

  • mythtv/libs/libmyth/audio/audiooutputalsa.cpp 

    From 779d08beeed45b765f3a696f209041d87bd9d5fd Mon Sep 17 00:00:00 2001
From: Lawrence Rust <lvr@softsystem.co.uk>
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 <lvr@softsystem.co.uk>
---
 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 b bool AudioOutputALSA::OpenMixer(void) 
    10111011QMap<QString, QString> *AudioOutputALSA::GetDevices(const char *type)
    10121012{
    10131013    QMap<QString, QString> *alsadevs = new QMap<QString, QString>();
    1014     void **hints, **n;
    1015     char *name, *desc;
    10161014
    1017     if (snd_device_name_hint(-1, type, &hints) < 0)
    1018         return alsadevs;
    1019     n = hints;
    1020 
    1021     while (*n != NULL)
     1015    // Loop through the sound cards to get Alsa device hints.
     1016    // NB Don't use snd_device_name_hint(-1,..) since there is a potential
     1017    // access violation using this ALSA API with libasound.so.2.0.0.
     1018    // See http://code.google.com/p/chromium/issues/detail?id=95797
     1019    int card = -1;
     1020    while (!snd_card_next(&card) && card >= 0)
    10221021    {
    1023           name = snd_device_name_get_hint(*n, "NAME");
    1024           desc = snd_device_name_get_hint(*n, "DESC");
    1025           if (name && desc && strcmp(name, "null"))
    1026               alsadevs->insert(name, desc);
    1027           if (name)
    1028               free(name);
    1029           if (desc)
    1030               free(desc);
    1031           n++;
     1022        void** hints = NULL;
     1023        int error = snd_device_name_hint(card, type, &hints);
     1024        if (error == 0)
     1025        {
     1026            void *hint;
     1027            for (int i = 0; (hint = hints[i]) != NULL; ++i)
     1028            {
     1029                char *name = snd_device_name_get_hint(hint, "NAME");
     1030                if (name)
     1031                {
     1032                    char *desc = snd_device_name_get_hint(hint, "DESC");
     1033                    if (desc)
     1034                    {
     1035                        if (strcmp(name, "null"))
     1036                            alsadevs->insert(name, desc);
     1037                        free(desc);
     1038                    }
     1039                    free(name);
     1040                }
     1041            }
     1042
     1043            snd_device_name_free_hint(hints);
     1044        }
     1045        else
     1046        {
     1047            VBERROR(QString("Failed to get device hints for card %1, error %2")
     1048                    .arg(card).arg(error));
     1049        }
    10321050    }
    1033     snd_device_name_free_hint(hints);
     1051
    10341052        // Work around ALSA bug < 1.0.22 ; where snd_device_name_hint can corrupt
    10351053        // global ALSA memory context
    10361054#if SND_LIB_MAJOR == 1