ipvs: fix racy memcpy in proc_do_sync_threshold

When two threads run proc_do_sync_threshold() in parallel,
data races could happen between the two memcpy():

Thread-1			Thread-2
memcpy(val, valp, sizeof(val));
				memcpy(valp, val, sizeof(val));

This race might mess up the (struct ctl_table *) table->data,
so we add a mutex lock to serialize them.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/netdev/B6988E90-0A1E-4B85-BF26-2DAF6D482433@gmail.com/
Signed-off-by: Sishuai Gong <sishuai.system@gmail.com>
Acked-by: Simon Horman <horms@kernel.org>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Florian Westphal <fw@strlen.de>

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 62606fb..4bb0d90 100644 (file)
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1876,6 +1876,7 @@ static int
 proc_do_sync_threshold(struct ctl_table *table, int write,
                       void *buffer, size_t *lenp, loff_t *ppos)
 {
+       struct netns_ipvs *ipvs = table->extra2;
        int *valp = table->data;
        int val[2];
        int rc;
@@ -1885,6 +1886,7 @@ proc_do_sync_threshold(struct ctl_table *table, int write,
                .mode = table->mode,
        };
 
+       mutex_lock(&ipvs->sync_mutex);
        memcpy(val, valp, sizeof(val));
        rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
        if (write) {
@@ -1894,6 +1896,7 @@ proc_do_sync_threshold(struct ctl_table *table, int write,
                else
                        memcpy(valp, val, sizeof(val));
        }
+       mutex_unlock(&ipvs->sync_mutex);
        return rc;
 }
 
@@ -4321,6 +4324,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
        ipvs->sysctl_sync_threshold[0] = DEFAULT_SYNC_THRESHOLD;
        ipvs->sysctl_sync_threshold[1] = DEFAULT_SYNC_PERIOD;
        tbl[idx].data = &ipvs->sysctl_sync_threshold;
+       tbl[idx].extra2 = ipvs;
        tbl[idx++].maxlen = sizeof(ipvs->sysctl_sync_threshold);
        ipvs->sysctl_sync_refresh_period = DEFAULT_SYNC_REFRESH_PERIOD;
        tbl[idx++].data = &ipvs->sysctl_sync_refresh_period;