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authorGao Feng <fgao@ikuai8.com>2017-03-24 07:05:12 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-22 09:23:22 +0100
commit37633f021b7f88a003ef57b334c9ac31509e89f9 (patch)
treed8dc7307e669db4528417bdcd03adadbfe895c96 /include
parentd074ae9505e4f9f811e4df37ec7136f2900ca1ae (diff)
tcp: sysctl: Fix a race to avoid unexpected 0 window from space
[ Upstream commit c48367427a39ea0b85c7cf018fe4256627abfd9e ] Because sysctl_tcp_adv_win_scale could be changed any time, so there is one race in tcp_win_from_space. For example, 1.sysctl_tcp_adv_win_scale<=0 (sysctl_tcp_adv_win_scale is negative now) 2.space>>(-sysctl_tcp_adv_win_scale) (sysctl_tcp_adv_win_scale is postive now) As a result, tcp_win_from_space returns 0. It is unexpected. Certainly if the compiler put the sysctl_tcp_adv_win_scale into one register firstly, then use the register directly, it would be ok. But we could not depend on the compiler behavior. Signed-off-by: Gao Feng <fgao@ikuai8.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/net/tcp.h8
1 files changed, 5 insertions, 3 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index cecb0e0eff06..a3696b778757 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1199,9 +1199,11 @@ void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
static inline int tcp_win_from_space(int space)
{
- return sysctl_tcp_adv_win_scale<=0 ?
- (space>>(-sysctl_tcp_adv_win_scale)) :
- space - (space>>sysctl_tcp_adv_win_scale);
+ int tcp_adv_win_scale = sysctl_tcp_adv_win_scale;
+
+ return tcp_adv_win_scale <= 0 ?
+ (space>>(-tcp_adv_win_scale)) :
+ space - (space>>tcp_adv_win_scale);
}
/* Note: caller must be prepared to deal with negative returns */