res_musiconhold: avoid moh state access on unlocked chan

Move channel unlock to after moh state access to avoid
potential unlocked access to state.

Resolves: #133

diff --git a/res/res_musiconhold.c b/res/res_musiconhold.c
index 9844de0cd0323ab3f2ebb8b1c8a62b485a9cb50f..a3305dbd5f575252d983a8fa128259054fa2ecd0 100644 (file)
--- a/res/res_musiconhold.c
+++ b/res/res_musiconhold.c
@@ -456,24 +456,22 @@ static void moh_files_write_format_change(struct ast_channel *chan, void *data)
 
 static int moh_files_generator(struct ast_channel *chan, void *data, int len, int samples)
 {
-       struct moh_files_state *state = ast_channel_music_state(chan);
+       struct moh_files_state *state;
        struct ast_frame *f = NULL;
-       int res = 0;
+       int res = 0, sample_queue = 0;
 
+       ast_channel_lock(chan);
+       state = ast_channel_music_state(chan);
        state->sample_queue += samples;
+       /* save the sample queue value for un-locked access */
+       sample_queue = state->sample_queue;
+       ast_channel_unlock(chan);
 
-       while (state->sample_queue > 0) {
+       while (sample_queue > 0) {
                ast_channel_lock(chan);
                f = moh_files_readframe(chan);
-
-               /* We need to be sure that we unlock
-                * the channel prior to calling
-                * ast_write. Otherwise, the recursive locking
-                * that occurs can cause deadlocks when using
-                * indirect channels, like local channels
-                */
-               ast_channel_unlock(chan);
                if (!f) {
+                       ast_channel_unlock(chan);
                        return -1;
                }
 
@@ -487,6 +485,19 @@ static int moh_files_generator(struct ast_channel *chan, void *data, int len, in
                if (ast_format_cmp(f->subclass.format, state->mohwfmt) == AST_FORMAT_CMP_NOT_EQUAL) {
                        ao2_replace(state->mohwfmt, f->subclass.format);
                }
+
+               /* We need to be sure that we unlock
+                * the channel prior to calling
+                * ast_write, but after our references to state
+                * as it refers to chan->music_state. Update
+                * sample_queue for our loop
+                * Otherwise, the recursive locking that occurs
+                * can cause deadlocks when using indirect
+                * channels, like local channels
+                */
+               sample_queue = state->sample_queue;
+               ast_channel_unlock(chan);
+
                res = ast_write(chan, f);
                ast_frfree(f);
                if (res < 0) {