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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 /Documentation
parent8475ef9fd16cadbfc692f78e608d1941a340beb2 (diff)
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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 'Documentation')
-rw-r--r--Documentation/networking/ip-sysctl.txt1
1 files changed, 1 insertions, 0 deletions
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index fe95105992c..3c5e465296e 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