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authorAlexey Dobriyan <adobriyan@gmail.com>2010-11-22 07:54:21 -0500
committerDavid S. Miller <davem@davemloft.net>2010-11-28 13:39:45 -0500
commit0147fc058d11bd4009b126d09974d2c8f48fef15 (patch)
treef73f0e82f7774938dd7190c6a810e0ccb2466f2b /net
parent8475ef9fd16cadbfc692f78e608d1941a340beb2 (diff)
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>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/sysctl_net_ipv4.c6
1 files changed, 5 insertions, 1 deletions
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;
26static int tcp_retr1_max = 255; 26static int tcp_retr1_max = 255;
27static int ip_local_port_range_min[] = { 1, 1 }; 27static int ip_local_port_range_min[] = { 1, 1 };
28static int ip_local_port_range_max[] = { 65535, 65535 }; 28static int ip_local_port_range_max[] = { 65535, 65535 };
29static int tcp_adv_win_scale_min = -31;
30static int tcp_adv_win_scale_max = 31;
29 31
30/* Update system visible IP port range */ 32/* Update system visible IP port range */
31static void set_local_port_range(int range[2]) 33static void set_local_port_range(int range[2])
@@ -426,7 +428,9 @@ static struct ctl_table ipv4_table[] = {
426 .data = &sysctl_tcp_adv_win_scale, 428 .data = &sysctl_tcp_adv_win_scale,
427 .maxlen = sizeof(int), 429 .maxlen = sizeof(int),
428 .mode = 0644, 430 .mode = 0644,
429 .proc_handler = proc_dointvec 431 .proc_handler = proc_dointvec_minmax,
432 .extra1 = &tcp_adv_win_scale_min,
433 .extra2 = &tcp_adv_win_scale_max,
430 }, 434 },
431 { 435 {
432 .procname = "tcp_tw_reuse", 436 .procname = "tcp_tw_reuse",