linux-kernel - Re: [PATCH] sysctl: Fix proc_do_large

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Date:   Wed, 20 Feb 2019 17:35:04 -0600
From:   Eric Sandeen <sandeen@...deen.net>
To:     Eric Sandeen <sandeen@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        fsdevel <linux-fsdevel@...r.kernel.org>, netdev@...r.kernel.org
Cc:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] sysctl: Fix proc_do_large_bitmap for large input buffers

Here's a pretty hacky test script to test this code via
ip_local_reserved_ports

-----

#!/bin/bash

# Randomly construct well-formed (sequential, non-overlapping)
# input for ip_local_reserved_ports, feed it to the sysctl,
# then read it back and check for differences.

# Port range to use
PORT_START=1024
PORT_STOP=32768

# Total length of ports string to use
LENGTH=$((4096+$((RANDOM % 16384))))

# String containing our list of ports
PORTS=$PORT_START

# Try 1000 times
for I in `seq 1 1000`; do
	
	# build up the string
	while true; do
		# Make sure it's discontiguous, skip ahead at least 2
		SKIP=$((2 + RANDOM % 10))
		PORT_START=$((PORT_START + SKIP))
	
		if [ "$PORT_START" -ge "$PORT_STOP" ]; then
			break;
		fi
	
		# 14856-14863,14861
		# Add a range, or a single port
		USERANGE=$((RANDOM % 2))
	
		if [ "$USERANGE" -eq "1" ]; then
			RANGE_START=$PORT_START
			RANGE_LEN=$((1 + RANDOM % 10))
			RANGE_END=$((RANGE_START + RANGE_LEN))
			PORTS="${PORTS},${RANGE_START}-${RANGE_END}"
			# Break out if we've done enough
			if [ "$RANGE_END" -eq "$PORT_STOP" ]; then
				break;
			fi
			PORT_START=$RANGE_END
		else
			PORTS="${PORTS},${PORT_START}"
		fi
	
		if [ "${#PORTS}" -gt "$LENGTH" ]; then
			break;
		fi
	
	done
	
	# See if we get out what we put in
	echo "Trial $I"
	echo $PORTS > port_list
	cat port_list > /proc/sys/net/ipv4/ip_local_reserved_ports || break
	cat /proc/sys/net/ipv4/ip_local_reserved_ports > port_list_out
	diff -uq port_list port_list_out || break
	
done