diff options
| author | Gao Feng <fgao@ikuai8.com> | 2017-03-24 07:05:12 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-22 09:17:43 +0100 |
| commit | 694f219a606f80811ea384044b9845c80d688bb3 (patch) | |
| tree | dbe5f8e02a60a2f56c9c1a88af4846fb86485440 /include | |
| parent | 84353d9d99cf6793f6f28e948f2973681d63806c (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.h | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index caf35e062639..18f029bcb8c7 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1265,9 +1265,11 @@ 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 */ |