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pbx.c: put copy of ast_exten.data on stack to prevent memory corruption

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During dialplan execution in pbx_extension_helper(), the contexts global
read lock prevents link list corruption, but was released with a pointer
to the ast_exten and data later used in variable substitution.  Instead,
this patch removes pbx_substitute_variables() and locates a copy of the
ast_exten data on the stack before releasing the lock, where ast_exten
could get free'd by another thread performing a module reload.

(issue AST-1179)
Reported by: Thomas Arimont
(issue AST-1246)
Reported by: Alexander Hömig
Review: https://reviewboard.asterisk.org/r/3055/
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Merged revisions 403862 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 403863 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 403864 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@403865 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Scott Griepentrog
2013-12-16 16:12:44 +00:00
parent 3322180d4b
commit 102d448486
1 changed files with 16 additions and 20 deletions
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36
main/pbx.c
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@@ -4627,25 +4627,6 @@ void pbx_substitute_variables_varshead(struct varshead *headp, const char *cp1,
pbx_substitute_variables_helper_full(NULL, headp, cp1, cp2, count, &used);
}
static void pbx_substitute_variables(char *passdata, int datalen, struct ast_channel *c, struct ast_exten *e)
{
const char *tmp;
/* Nothing more to do */
if (!e->data) {
*passdata = '\0';
return;
}
/* No variables or expressions in e->data, so why scan it? */
if ((!(tmp = strchr(e->data, '$'))) || (!strstr(tmp, "${") && !strstr(tmp, "$["))) {
ast_copy_string(passdata, e->data, datalen);
return;
}
pbx_substitute_variables_helper(c, e->data, passdata, datalen - 1);
}
/*!
* \brief The return value depends on the action:
*
@@ -4670,6 +4651,7 @@ static int pbx_extension_helper(struct ast_channel *c, struct ast_context *con,
{
struct ast_exten *e;
struct ast_app *app;
char *substitute = NULL;
int res;
struct pbx_find_info q = { .stacklen = 0 }; /* the rest is reset in pbx_find_extension */
char passdata[EXT_DATA_SIZE];
@@ -4696,6 +4678,18 @@ static int pbx_extension_helper(struct ast_channel *c, struct ast_context *con,
if (!e->cached_app)
e->cached_app = pbx_findapp(e->app);
app = e->cached_app;
if (ast_strlen_zero(e->data)) {
*passdata = '\0';
} else {
const char *tmp;
if ((!(tmp = strchr(e->data, '$'))) || (!strstr(tmp, "${") && !strstr(tmp, "$["))) {
/* no variables to substitute, copy on through */
ast_copy_string(passdata, e->data, sizeof(passdata));
} else {
/* save e->data on stack for later processing after lock released */
substitute = ast_strdupa(e->data);
}
}
ast_unlock_contexts();
if (!app) {
ast_log(LOG_WARNING, "No application '%s' for extension (%s, %s, %d)\n", e->app, context, exten, priority);
@@ -4706,7 +4700,9 @@ static int pbx_extension_helper(struct ast_channel *c, struct ast_context *con,
if (ast_channel_exten(c) != exten)
ast_channel_exten_set(c, exten);
ast_channel_priority_set(c, priority);
pbx_substitute_variables(passdata, sizeof(passdata), c, e);
if (substitute) {
pbx_substitute_variables_helper(c, substitute, passdata, sizeof(passdata)-1);
}
ast_debug(1, "Launching '%s'\n", app->name);
{
ast_verb(3, "Executing [%s@%s:%d] " COLORIZE_FMT "(\"" COLORIZE_FMT "\", \"" COLORIZE_FMT "\") %s\n",