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authorAlexey Dobriyan <adobriyan@gmail.com>2010-11-22 12:54:21 +0000
committerDavid S. Miller <davem@davemloft.net>2010-11-28 10:39:45 -0800
commit0147fc058d11bd4009b126d09974d2c8f48fef15 (patch)
treef73f0e82f7774938dd7190c6a810e0ccb2466f2b
parent8475ef9fd16cadbfc692f78e608d1941a340beb2 (diff)
downloadop-kernel-dev-0147fc058d11bd4009b126d09974d2c8f48fef15.zip
op-kernel-dev-0147fc058d11bd4009b126d09974d2c8f48fef15.tar.gz
tcp: restrict net.ipv4.tcp_adv_win_scale (#20312)
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> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--Documentation/networking/ip-sysctl.txt1
-rw-r--r--net/ipv4/sysctl_net_ipv4.c6
2 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index fe951059..3c5e465 100644
--- 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
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e91911d..1b4ec21 100644
--- 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",
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