* [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312)
@ 2010-11-14 15:18 Alexey Dobriyan
2010-11-14 19:49 ` Eric Dumazet
0 siblings, 1 reply; 6+ messages in thread
From: Alexey Dobriyan @ 2010-11-14 15:18 UTC (permalink / raw)
To: davem; +Cc: shemminger, netdev
tcp_win_from_space() does the following:
if (sysctl_tcp_adv_win_scale <= 0)
return space >> (-sysctl_tcp_adv_win_scale);
else
return space - (space >> sysctl_tcp_adv_win_scale);
"space" is int.
As per C99 6.5.7 (3) shifting int for 32 or more bits is
undefined behaviour.
Indeed, if sysctl_tcp_adv_win_scale is exactly 32, space >> 32 equals
space and function returns 0;
Which means we busyloop in tcp_fixup_rcvbuf().
Restrict net.ipv4.tcp_adv_win_scale to [-31, 31].
Fix https://bugzilla.kernel.org/show_bug.cgi?id=20312
Steps to reproduce:
echo 32 >/proc/sys/net/ipv4/tcp_adv_win_scale
wget www.kernel.org
[softlockup]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -26,6 +26,8 @@ static int zero;
static int tcp_retr1_max = 255;
static int ip_local_port_range_min[] = { 1, 1 };
static int ip_local_port_range_max[] = { 65535, 65535 };
+static int _minus_31 = -31;
+static int _31 = 31;
/* Update system visible IP port range */
static void set_local_port_range(int range[2])
@@ -426,7 +428,9 @@ static struct ctl_table ipv4_table[] = {
.data = &sysctl_tcp_adv_win_scale,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &_minus_31,
+ .extra2 = &_31,
},
{
.procname = "tcp_tw_reuse",
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312)
2010-11-14 15:18 [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312) Alexey Dobriyan
@ 2010-11-14 19:49 ` Eric Dumazet
2010-11-14 20:14 ` Alexey Dobriyan
0 siblings, 1 reply; 6+ messages in thread
From: Eric Dumazet @ 2010-11-14 19:49 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: davem, shemminger, netdev
Le dimanche 14 novembre 2010 à 17:18 +0200, Alexey Dobriyan a écrit :
> tcp_win_from_space() does the following:
>
> if (sysctl_tcp_adv_win_scale <= 0)
> return space >> (-sysctl_tcp_adv_win_scale);
> else
> return space - (space >> sysctl_tcp_adv_win_scale);
>
> "space" is int.
>
> As per C99 6.5.7 (3) shifting int for 32 or more bits is
> undefined behaviour.
>
> Indeed, if sysctl_tcp_adv_win_scale is exactly 32, space >> 32 equals
> space and function returns 0;
>
> Which means we busyloop in tcp_fixup_rcvbuf().
>
> Restrict net.ipv4.tcp_adv_win_scale to [-31, 31].
>
> Fix https://bugzilla.kernel.org/show_bug.cgi?id=20312
>
> Steps to reproduce:
>
> echo 32 >/proc/sys/net/ipv4/tcp_adv_win_scale
> wget www.kernel.org
> [softlockup]
>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>
Please fix your patch title, you speak of adv_min_scale ...
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -26,6 +26,8 @@ static int zero;
> static int tcp_retr1_max = 255;
> static int ip_local_port_range_min[] = { 1, 1 };
> static int ip_local_port_range_max[] = { 65535, 65535 };
> +static int _minus_31 = -31;
> +static int _31 = 31;
Please use normal symbols, not starting by underscore.
>
> /* Update system visible IP port range */
> static void set_local_port_range(int range[2])
> @@ -426,7 +428,9 @@ static struct ctl_table ipv4_table[] = {
> .data = &sysctl_tcp_adv_win_scale,
> .maxlen = sizeof(int),
> .mode = 0644,
> - .proc_handler = proc_dointvec
> + .proc_handler = proc_dointvec_minmax,
> + .extra1 = &_minus_31,
> + .extra2 = &_31,
> },
> {
> .procname = "tcp_tw_reuse",
Please change Documentation/networking/ip-sysctl.txt to reflect possible
values of adv_win_scale
Thanks
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312)
2010-11-14 19:49 ` Eric Dumazet
@ 2010-11-14 20:14 ` Alexey Dobriyan
2010-11-15 14:18 ` Ben Hutchings
0 siblings, 1 reply; 6+ messages in thread
From: Alexey Dobriyan @ 2010-11-14 20:14 UTC (permalink / raw)
To: Eric Dumazet; +Cc: davem, shemminger, netdev
On Sun, Nov 14, 2010 at 08:49:43PM +0100, Eric Dumazet wrote:
> > +static int _minus_31 = -31;
> > +static int _31 = 31;
>
> Please use normal symbols, not starting by underscore.
static int thirty_one = 31? :-)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312)
2010-11-14 20:14 ` Alexey Dobriyan
@ 2010-11-15 14:18 ` Ben Hutchings
2010-11-22 22:54 ` [PATCH v2] tcp: restrict net.ipv4.tcp_adv_win_scale (#20312) Alexey Dobriyan
0 siblings, 1 reply; 6+ messages in thread
From: Ben Hutchings @ 2010-11-15 14:18 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: Eric Dumazet, davem, shemminger, netdev
On Sun, 2010-11-14 at 22:14 +0200, Alexey Dobriyan wrote:
> On Sun, Nov 14, 2010 at 08:49:43PM +0100, Eric Dumazet wrote:
> > > +static int _minus_31 = -31;
> > > +static int _31 = 31;
> >
> > Please use normal symbols, not starting by underscore.
>
> static int thirty_one = 31? :-)
How about, oh, I don't know, adv_win_scale_{min,max}?
Ben.
--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v2] tcp: restrict net.ipv4.tcp_adv_win_scale (#20312)
2010-11-15 14:18 ` Ben Hutchings
@ 2010-11-22 22:54 ` Alexey Dobriyan
2010-11-28 18:39 ` David Miller
0 siblings, 1 reply; 6+ messages in thread
From: Alexey Dobriyan @ 2010-11-22 22:54 UTC (permalink / raw)
To: davem; +Cc: Eric Dumazet, shemminger, netdev, Ben Hutchings
tcp_win_from_space() does the following:
if (sysctl_tcp_adv_win_scale <= 0)
return space >> (-sysctl_tcp_adv_win_scale);
else
return space - (space >> sysctl_tcp_adv_win_scale);
"space" is int.
As per C99 6.5.7 (3) shifting int for 32 or more bits is
undefined behaviour.
Indeed, if sysctl_tcp_adv_win_scale is exactly 32,
space >> 32 equals space and function returns 0.
Which means we busyloop in tcp_fixup_rcvbuf().
Restrict net.ipv4.tcp_adv_win_scale to [-31, 31].
Fix https://bugzilla.kernel.org/show_bug.cgi?id=20312
Steps to reproduce:
echo 32 >/proc/sys/net/ipv4/tcp_adv_win_scale
wget www.kernel.org
[softlockup]
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---
Documentation/networking/ip-sysctl.txt | 1 +
net/ipv4/sysctl_net_ipv4.c | 6 +++++-
2 files changed, 6 insertions(+), 1 deletion(-)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -144,6 +144,7 @@ tcp_adv_win_scale - INTEGER
Count buffering overhead as bytes/2^tcp_adv_win_scale
(if tcp_adv_win_scale > 0) or bytes-bytes/2^(-tcp_adv_win_scale),
if it is <= 0.
+ Possible values are [-31, 31], inclusive.
Default: 2
tcp_allowed_congestion_control - STRING
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -26,6 +26,8 @@ static int zero;
static int tcp_retr1_max = 255;
static int ip_local_port_range_min[] = { 1, 1 };
static int ip_local_port_range_max[] = { 65535, 65535 };
+static int tcp_adv_win_scale_min = -31;
+static int tcp_adv_win_scale_max = 31;
/* Update system visible IP port range */
static void set_local_port_range(int range[2])
@@ -426,7 +428,9 @@ static struct ctl_table ipv4_table[] = {
.data = &sysctl_tcp_adv_win_scale,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = &tcp_adv_win_scale_min,
+ .extra2 = &tcp_adv_win_scale_max,
},
{
.procname = "tcp_tw_reuse",
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH v2] tcp: restrict net.ipv4.tcp_adv_win_scale (#20312)
2010-11-22 22:54 ` [PATCH v2] tcp: restrict net.ipv4.tcp_adv_win_scale (#20312) Alexey Dobriyan
@ 2010-11-28 18:39 ` David Miller
0 siblings, 0 replies; 6+ messages in thread
From: David Miller @ 2010-11-28 18:39 UTC (permalink / raw)
To: adobriyan; +Cc: eric.dumazet, shemminger, netdev, bhutchings
From: Alexey Dobriyan <adobriyan@gmail.com>
Date: Tue, 23 Nov 2010 00:54:21 +0200
> tcp_win_from_space() does the following:
>
> if (sysctl_tcp_adv_win_scale <= 0)
> return space >> (-sysctl_tcp_adv_win_scale);
> else
> return space - (space >> sysctl_tcp_adv_win_scale);
>
> "space" is int.
>
> As per C99 6.5.7 (3) shifting int for 32 or more bits is
> undefined behaviour.
>
> Indeed, if sysctl_tcp_adv_win_scale is exactly 32,
> space >> 32 equals space and function returns 0.
>
> Which means we busyloop in tcp_fixup_rcvbuf().
>
> Restrict net.ipv4.tcp_adv_win_scale to [-31, 31].
>
> Fix https://bugzilla.kernel.org/show_bug.cgi?id=20312
>
> Steps to reproduce:
>
> echo 32 >/proc/sys/net/ipv4/tcp_adv_win_scale
> wget www.kernel.org
> [softlockup]
>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
I'll aply this, thanks Alexey.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2010-11-28 18:38 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2010-11-14 15:18 [PATCH] tcp: restrict net.ipv4.tcp_adv_min_scale (#20312) Alexey Dobriyan
2010-11-14 19:49 ` Eric Dumazet
2010-11-14 20:14 ` Alexey Dobriyan
2010-11-15 14:18 ` Ben Hutchings
2010-11-22 22:54 ` [PATCH v2] tcp: restrict net.ipv4.tcp_adv_win_scale (#20312) Alexey Dobriyan
2010-11-28 18:39 ` David Miller
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