[LEDE-DEV] Bug when processing long lines

[Jakub Horák]

Hello LEDE developers,

I found a bug in procd that gets triggered when long lines are printed
by services whose stdout/stderr are being logged. The bug itself is
explained in the attached patch.

However, when I was testing the fix, I found out that the bug is present
in other places, mostly those that call "ustream_get_read_buf" function.
Some examples:

- ubox/log/logread.c:logread_fb_data_cb() - when buffer passed on the
descriptor is larger than 4096, reception stops
- netifd/main.c:netifd_process_log_read_cb - this is a place that seems
to have this bug fixed, but still has incorrect handling of NUL bytes
- libubox/examples/ustream-example.c:client_read_cb - this is probably
the place that originated this broken bit of code
- uhttpd/relay.c:relay_process_headers - another place that seems broken

I've attached an init script (that goes to /etc/init.d/flood) and three
Lua programs (flood[123].lua) that trigger this behavior:
- flood1.lua writes long message to stdout, that triggers this behavior
in procd
- flood2.lua writes message that gets correctly processed by procd, but
triggers the bug in logread
- flood3.lua writes message with embedded zeros

I don't post patches to mailing lists very often, so I apologize if I'm
sending this in a wrong format or in a too broken english.

Best regards,
Jakub Horak
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#!/bin/sh /etc/rc.common

START=99

USE_PROCD=1
PROG=/bin/flood1.lua

start_service()
{
	config_load cgminer

	procd_open_instance
	procd_set_param command "$PROG" 
	procd_set_param respawn ${respawn_threshold:-3600} ${respawn_timeout:-5} ${respawn_retry:-0}
	procd_set_param stdout 1
	procd_set_param stderr 1
	procd_close_instance
}

stop_service()
{
	echo stop
}

service_triggers()
{
	procd_add_reload_trigger "flood"
}
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