提交 c4836742 编写于 作者: G Gao Feng 提交者: David S. Miller

tcp: sysctl: Fix a race to avoid unexpected 0 window from space

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: NGao Feng <fgao@ikuai8.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
上级 e013fb7c
......@@ -1248,9 +1248,11 @@ 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 */
......
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