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Simon Horman wrote:
> On Mon, Aug 31, 2009 at 02:22:26PM +0200, Patrick McHardy wrote:
>> It seems that proc_do_sync_threshold() should check whether this value
>> is zero. The current checks also look racy since incorrect values are
>> first updated, then overwritten again.
>
> I'm wondering if an approach along the lines of the following is valid.
> The idea is that the value in the ctl_table is essentially a scratch
> value that is used by the parser and then copied into ip_vs_sync_threshold
> if it is valid.
Even simpler would be to use a temporary buffer on the stack for copying
the values from userspace and then copy them to the final buffer after
validation.
> I'm concerned that there are atomicity issues
> surrounding writing ip_vs_sync_threshold while there might be readers.
That might be a problem if they are required to be "synchronized".
> --- a/net/netfilter/ipvs/ip_vs_core.c
> +++ b/net/netfilter/ipvs/ip_vs_core.c
> @@ -1362,8 +1362,7 @@ ip_vs_in(unsigned int hooknum, struct sk_buff *skb,
> (ip_vs_sync_state & IP_VS_STATE_MASTER) &&
> (((cp->protocol != IPPROTO_TCP ||
> cp->state == IP_VS_TCP_S_ESTABLISHED) &&
> - (pkts % sysctl_ip_vs_sync_threshold[1]
> - == sysctl_ip_vs_sync_threshold[0])) ||
> + (pkts % ip_vs_sync_threshold[1] == ip_vs_sync_threshold[0])) ||
> ((cp->protocol == IPPROTO_TCP) && (cp->old_state != cp->state) &&
> ((cp->state == IP_VS_TCP_S_FIN_WAIT) ||
> (cp->state == IP_VS_TCP_S_CLOSE_WAIT) ||
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index fba2892..8a9ff21 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -76,6 +76,11 @@ static atomic_t ip_vs_dropentry = ATOMIC_INIT(0);
> /* number of virtual services */
> static int ip_vs_num_services = 0;
>
> +/* threshold handling */
> +static int ip_vs_sync_threshold_min = 0;
> +static int ip_vs_sync_threshold_max = INT_MAX;
> +int ip_vs_sync_threshold[2] = { 3, 50 };
> +
min should be 1 I guess or you still need to manually check
that ip_vs_sync_threshold[1] != 0 to avoid a division be zero.
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