Bug 20312

Summary:	System freeze with multiples of 32 in /proc/sys/net/ipv4/tcp_adv_win_scale
Product:	Networking	Reporter:	Tobias Schmidbauer (tobs651)
Component:	IPV4	Assignee:	Alexey Dobriyan (adobriyan)
Status:	CLOSED CODE_FIX
Severity:	normal	CC:	adobriyan, florian, martin.steigerwald, Martin
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.36-rc6	Subsystem:
Regression:	No	Bisected commit-id:

Description Tobias Schmidbauer 2010-10-14 14:43:15 UTC

System freezes when setting /proc/sys/net/ipv4/tcp_adv_win_scale to a multiple of 32 and causing network traffic (for example ssh, wget, firefox, etc). Does NOT happen with ping

It also happens with kernel 2.6.26 (debian lenny). 

there is no output via dmesg, no logging about any system events in /var/log/messages or /var/log/syslog and nothing or on tty1



for example 

echo 32 > /proc/sys/net/ipv4/tcp_adv_win_scale
wget www.kernel.org



I tested
16 >> working
32 >> freeze
33 >> working
31 >> working
64 >> freeze
65 >> working
96 >> freeze
128 >> freeze

Comment 1 Tobias Schmidbauer 2010-10-14 14:49:04 UTC

Identical results on 32bit and 64bit systems

Comment 2 Alexey Dobriyan 2010-12-07 15:57:52 UTC

fixed in 2.6.37-rc4
"tcp: restrict net.ipv4.tcp_adv_win_scale (#20312)"

Comment 3 Martin Steigerwald 2010-12-07 21:14:18 UTC

Thanks a lot, Alexey.

Verified:

shambhala:~#1> LANG=C echo 32 > /proc/sys/net/ipv4/tcp_adv_win_scale
echo: write error: invalid argument
shambhala:~#1> LANG=C echo 31 > /proc/sys/net/ipv4/tcp_adv_win_scale
shambhala:~> LANG=C echo -31 > /proc/sys/net/ipv4/tcp_adv_win_scale
shambhala:~> LANG=C echo -32 > /proc/sys/net/ipv4/tcp_adv_win_scale
echo: write error: invalid argument

On 2.6.37-rc5.

Comment 4 Florian Mickler 2011-01-23 16:22:33 UTC

commit 0147fc058d11bd4009b126d09974d2c8f48fef15
Author: Alexey Dobriyan <adobriyan@gmail.com>
Date:   Mon Nov 22 12:54:21 2010 +0000

    tcp: restrict net.ipv4.tcp_adv_win_scale (#20312)