diff options
| author | Eric Dumazet <eric.dumazet@gmail.com> | 2010-12-07 13:20:47 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2010-12-08 21:34:09 +0100 |
| commit | f19872575ff7819a3723154657a497d9bca66b33 (patch) | |
| tree | 3c84b591c773611a6c4c00589f69a6639e83b8e0 /net/ipv4/tcp_output.c | |
| parent | tcp: avoid a possible divide by zero (diff) | |
| download | linux-f19872575ff7819a3723154657a497d9bca66b33.tar.xz linux-f19872575ff7819a3723154657a497d9bca66b33.zip | |
tcp: protect sysctl_tcp_cookie_size reads
Make sure sysctl_tcp_cookie_size is read once in
tcp_cookie_size_check(), or we might return an illegal value to caller
if sysctl_tcp_cookie_size is changed by another cpu.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Cc: William Allen Simpson <william.allen.simpson@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0d4a3cebfb46..61c2463e2753 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -385,27 +385,30 @@ struct tcp_out_options { */ static u8 tcp_cookie_size_check(u8 desired) { - if (desired > 0) { + int cookie_size; + + if (desired > 0) /* previously specified */ return desired; - } - if (sysctl_tcp_cookie_size <= 0) { + + cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size); + if (cookie_size <= 0) /* no default specified */ return 0; - } - if (sysctl_tcp_cookie_size <= TCP_COOKIE_MIN) { + + if (cookie_size <= TCP_COOKIE_MIN) /* value too small, specify minimum */ return TCP_COOKIE_MIN; - } - if (sysctl_tcp_cookie_size >= TCP_COOKIE_MAX) { + + if (cookie_size >= TCP_COOKIE_MAX) /* value too large, specify maximum */ return TCP_COOKIE_MAX; - } - if (0x1 & sysctl_tcp_cookie_size) { + + if (cookie_size & 1) /* 8-bit multiple, illegal, fix it */ - return (u8)(sysctl_tcp_cookie_size + 0x1); - } - return (u8)sysctl_tcp_cookie_size; + cookie_size++; + + return (u8)cookie_size; } /* Write previously computed TCP options to the packet. |