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Date: Wed, 24 Sep 2014 07:50:01 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Cc: Justin Cormack <justin@...cialbusservice.com>
Subject: Re: LUA + musl, garbage collection issue?
* Scott Valentine <scottvalen@...mail.com> [2014-09-23 19:25:47 -1000]:
>
> In any case, this has been a nasty issue to track down. I have surely traced it to the following code block in luci (by process of elimination):
>
> local fp
> luci.http.setfilehandler(
> function(meta, chunk, eof)
> if not fp then
> if meta and meta.name == "image" then
> fp = io.open(image_tmp, "w")
> else
> fp = io.popen(restore_tmp, "w")
> end
> end
> if chunk then
> fp:write(chunk)
> end
> if eof then
> fp:close()
> end
> end
> )
>
>
> Here, "chunk" is a 2048 byte string, and the library calls are to nixio:
>
are you sure the nixio function is called?
if fp is not set then io.open is called which should
use libc fopen, so fp:write should be a wrapper around
fwrite
if the code really calls the nixio function below then
there is no stdio involved, it directly writes to an fd
> static int nixio_file_write(lua_State *L) {
> int fd = nixio__checkfd(L, 1);
> size_t len;
> ssize_t sent;
> const char *data = luaL_checklstring(L, 2, &len);
>
> if (lua_gettop(L) > 2) {
> int offset = luaL_optint(L, 3, 0);
> if (offset) {
> if (offset < len) {
> data += offset;
> len -= offset;
> } else {
> len = 0;
> }
> }
>
> unsigned int wlen = luaL_optint(L, 4, len);
> if (wlen < len) {
> len = wlen;
> }
> }
>
> do {
> sent = write(fd, data, len);
> } while(sent == -1 && errno == EINTR);
> if (sent >= 0) {
> lua_pushinteger(L, sent);
> return 1;
> } else {
> return nixio__perror(L);
> }
> }
>
> When I have time, I'll do a build against eglibc with a reduced BUFSIZ = 1024 (musl's default) and see if the problem is reproduced.
>
i think you should try to reproduce the bug with a minimal
test-case where either stdio (io.*) is called or nixio only
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