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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2010-11-22 12:54:21 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-11-28 10:39:45 -0800 |
| commit | 0147fc058d11bd4009b126d09974d2c8f48fef15 (patch) | |
| tree | f73f0e82f7774938dd7190c6a810e0ccb2466f2b | |
| parent | 8475ef9fd16cadbfc692f78e608d1941a340beb2 (diff) | |
| download | linux-0147fc058d11bd4009b126d09974d2c8f48fef15.tar.gz linux-0147fc058d11bd4009b126d09974d2c8f48fef15.tar.xz | |
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.txt | 1 | ||||
| -rw-r--r-- | net/ipv4/sysctl_net_ipv4.c | 6 |
2 files changed, 6 insertions, 1 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index fe95105992c5..3c5e465296e1 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 e91911d7aae2..1b4ec21497a4 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", |