Merged revisions 88805 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
r88805 | russell | 2007-11-05 16:07:54 -0600 (Mon, 05 Nov 2007) | 12 lines

After seeing crashes related to channel variables, I went looking around at the
ways that channel variables are handled.  In general, they were not handled in
a thread-safe way.  The channel _must_ be locked when reading or writing from/to
the channel variable list.

What I have done to improve this situation is to make pbx_builtin_setvar_helper()
and friends lock the channel when doing their thing.  Asterisk API calls almost 
all lock the channel for you as necessary, but this family of functions did not.

(closes issue #10923, reported by atis)
(closes issue #11159, reported by 850t)

........


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@88934 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 37 insertions, 11 deletions

diff --git a/main/pbx.c b/main/pbx.c
index 71190ae9a..aa4459d35 100644
--- a/main/pbx.c
+++ b/main/pbx.c
@@ -1187,6 +1187,7 @@ void pbx_retrieve_variable(struct ast_channel *c, const char *var, char **ret, c
 	struct varshead *places[2] = { headp, &globals };	/* list of places where we may look */
 
 	if (c) {
+		ast_channel_lock(c);
 		places[0] = &c->varshead;
 	}
 	/*
@@ -1284,6 +1285,9 @@ void pbx_retrieve_variable(struct ast_channel *c, const char *var, char **ret, c
 		if (need_substring)
 			*ret = substring(*ret, offset, length, workspace, workspacelen);
 	}
+
+	if (c)
+		ast_channel_unlock(c);
 }
 
 static void exception_store_free(void *data)
@@ -5913,6 +5917,8 @@ int pbx_builtin_serialize_variables(struct ast_channel *chan, struct ast_str **b
 	(*buf)->used = 0;
 	(*buf)->str[0] = '\0';
 
+	ast_channel_lock(chan);
+
 	AST_LIST_TRAVERSE(&chan->varshead, variables, entries) {
 		if ((var = ast_var_name(variables)) && (val = ast_var_value(variables))
 		   /* && !ast_strlen_zero(var) && !ast_strlen_zero(val) */
@@ -5926,6 +5932,8 @@ int pbx_builtin_serialize_variables(struct ast_channel *chan, struct ast_str **b
 			break;
 	}
 
+	ast_channel_unlock(chan);
+
 	return total;
 }
 
@@ -5938,8 +5946,11 @@ const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name
 
 	if (!name)
 		return NULL;
-	if (chan)
+
+	if (chan) {
+		ast_channel_lock(chan);
 		places[0] = &chan->varshead;
+	}
 
 	for (i = 0; i < 2; i++) {
 		if (!places[i])
@@ -5958,6 +5969,9 @@ const char *pbx_builtin_getvar_helper(struct ast_channel *chan, const char *name
 			break;
 	}
 
+	if (chan)
+		ast_channel_unlock(chan);
+
 	return ret;
 }
 
@@ -5974,18 +5988,25 @@ void pbx_builtin_pushvar_helper(struct ast_channel *chan, const char *name, cons
 		return;
 	}
 
-	headp = (chan) ? &chan->varshead : &globals;
+	if (chan) {
+		ast_channel_lock(chan);
+		headp = &chan->varshead;
+	} else {
+		ast_rwlock_wrlock(&globalslock);
+		headp = &globals;
+	}
 
 	if (value) {
 		if (headp == &globals)
 			ast_verb(2, "Setting global variable '%s' to '%s'\n", name, value);
 		newvariable = ast_var_assign(name, value);
-		if (headp == &globals)
-			ast_rwlock_wrlock(&globalslock);
 		AST_LIST_INSERT_HEAD(headp, newvariable, entries);
-		if (headp == &globals)
-			ast_rwlock_unlock(&globalslock);
 	}
+
+	if (chan)
+		ast_channel_unlock(chan);
+	else
+		ast_rwlock_unlock(&globalslock);
 }
 
 void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const char *value)
@@ -5994,7 +6015,6 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 	struct varshead *headp;
 	const char *nametail = name;
 
-	/* XXX may need locking on the channel ? */
 	if (name[strlen(name) - 1] == ')') {
 		char *function = ast_strdupa(name);
 
@@ -6002,7 +6022,13 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 		return;
 	}
 
-	headp = (chan) ? &chan->varshead : &globals;
+	if (chan) {
+		ast_channel_lock(chan);
+		headp = &chan->varshead;
+	} else {
+		ast_rwlock_wrlock(&globalslock);
+		headp = &globals;
+	}
 
 	/* For comparison purposes, we have to strip leading underscores */
 	if (*nametail == '_') {
@@ -6011,8 +6037,6 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 			nametail++;
 	}
 
-	if (headp == &globals)
-		ast_rwlock_wrlock(&globalslock);
 	AST_LIST_TRAVERSE (headp, newvariable, entries) {
 		if (strcasecmp(ast_var_name(newvariable), nametail) == 0) {
 			/* there is already such a variable, delete it */
@@ -6036,7 +6060,9 @@ void pbx_builtin_setvar_helper(struct ast_channel *chan, const char *name, const
 			chan ? chan->uniqueid : "none");
 	}
 
-	if (headp == &globals)
+	if (chan)
+		ast_channel_unlock(chan);
+	else
 		ast_rwlock_unlock(&globalslock);
 }