diff options
| author | Gao Feng <fgao@ikuai8.com> | 2017-03-24 07:05:12 +0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-03-24 13:29:16 -0700 |
| commit | c48367427a39ea0b85c7cf018fe4256627abfd9e (patch) | |
| tree | 740f51767793ae5765a0ecedc931c1704d0bbf06 /include/net/tcp.h | |
| parent | e013fb7c4c9fa8aa914d85d8b466c990b2eaebb6 (diff) | |
| download | lwn-c48367427a39ea0b85c7cf018fe4256627abfd9e.tar.gz lwn-c48367427a39ea0b85c7cf018fe4256627abfd9e.zip | |
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: Gao Feng <fgao@ikuai8.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/tcp.h')
| -rw-r--r-- | include/net/tcp.h | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index e614ad4d613e..582e3772c0d9 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -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 */ |