BUG/MEDIUM: lua: segfault if a converter or a sample doesn't return anything
In the case of a Lua sample-fetch or converter doesn't return any
value, an acces outside the Lua stack can be performed. This patch
check the stack size before converting the top value to a HAProxy
internal sample.
A workaround consist to check that a value value is always returned
with sample fetches and converters.
This patch should be backported in the version 1.6 and 1.7
diff --git a/src/hlua.c b/src/hlua.c
index 643d3fc..b8d2c88 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -5496,6 +5496,10 @@
switch (hlua_ctx_resume(stream->hlua, 0)) {
/* finished. */
case HLUA_E_OK:
+ /* If the stack is empty, the function fails. */
+ if (lua_gettop(stream->hlua->T) <= 0)
+ return 0;
+
/* Convert the returned value in sample. */
hlua_lua2smp(stream->hlua->T, -1, smp);
lua_pop(stream->hlua->T, 1);
@@ -5617,6 +5621,10 @@
stream_int_retnclose(&stream->si[0], &msg);
return 0;
}
+ /* If the stack is empty, the function fails. */
+ if (lua_gettop(stream->hlua->T) <= 0)
+ return 0;
+
/* Convert the returned value in sample. */
hlua_lua2smp(stream->hlua->T, -1, smp);
lua_pop(stream->hlua->T, 1);