[PATCH net] ipvs: Improve robustness to the ipvs sysctl

[hujunwei <hujunwei4@xxxxxxxxxx>]

From: Junwei Hu <hujunwei4@xxxxxxxxxx>

The ipvs module parse the user buffer and save it to sysctl,
then check if the value is valid. invalid value occurs
over a period of time.
Here, I add a variable, struct ctl_table tmp, used to read
the value from the user buffer, and save only when it is valid.

Fixes: f73181c8288f ("ipvs: add support for sync threads")
Signed-off-by: Junwei Hu <hujunwei4@xxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 61 +++++++++++++++++++++++-----------
 1 file changed, 42 insertions(+), 19 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 741d91aa4a8d..e78fd05f108b 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1680,12 +1680,18 @@ proc_do_defense_mode(struct ctl_table *table, int write,
        int val = *valp;
        int rc;

-       rc = proc_dointvec(table, write, buffer, lenp, ppos);
+       struct ctl_table tmp = {
+               .data = &val,
+               .maxlen = sizeof(int),
+               .mode = table->mode,
+       };
+
+       rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
        if (write && (*valp != val)) {
-               if ((*valp < 0) || (*valp > 3)) {
-                       /* Restore the correct value */
+               if (val < 0 || val > 3)
+                       rc = -EINVAL;
+               else {
                        *valp = val;
-               } else {
                        update_defense_level(ipvs);
                }
        }
@@ -1699,15 +1705,20 @@ proc_do_sync_threshold(struct ctl_table *table, int 
write,
        int *valp = table->data;
        int val[2];
        int rc;
+       struct ctl_table tmp = {
+               .data = &val,
+               .maxlen = table->maxlen,
+               .mode = table->mode,
+       };

-       /* backup the value first */
        memcpy(val, valp, sizeof(val));
-
-       rc = proc_dointvec(table, write, buffer, lenp, ppos);
-       if (write && (valp[0] < 0 || valp[1] < 0 ||
-           (valp[0] >= valp[1] && valp[1]))) {
-               /* Restore the correct value */
-               memcpy(valp, val, sizeof(val));
+       rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
+       if (write) {
+               if (val[0] < 0 || val[1] < 0 ||
+                   (val[0] >= val[1] && val[1]))
+                       rc = -EINVAL;
+               else
+                       memcpy(valp, val, sizeof(val));
        }
        return rc;
 }
@@ -1720,12 +1731,18 @@ proc_do_sync_mode(struct ctl_table *table, int write,
        int val = *valp;
        int rc;

-       rc = proc_dointvec(table, write, buffer, lenp, ppos);
+       struct ctl_table tmp = {
+               .data = &val,
+               .maxlen = sizeof(int),
+               .mode = table->mode,
+       };
+
+       rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
        if (write && (*valp != val)) {
-               if ((*valp < 0) || (*valp > 1)) {
-                       /* Restore the correct value */
+               if (val < 0 || val > 1)
+                       rc = -EINVAL;
+               else
                        *valp = val;
-               }
        }
        return rc;
 }
@@ -1738,12 +1755,18 @@ proc_do_sync_ports(struct ctl_table *table, int write,
        int val = *valp;
        int rc;

-       rc = proc_dointvec(table, write, buffer, lenp, ppos);
+       struct ctl_table tmp = {
+               .data = &val,
+               .maxlen = sizeof(int),
+               .mode = table->mode,
+       };
+
+       rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
        if (write && (*valp != val)) {
-               if (*valp < 1 || !is_power_of_2(*valp)) {
-                       /* Restore the correct value */
+               if (val < 1 || !is_power_of_2(val))
+                       rc = -EINVAL;
+               else
                        *valp = val;
-               }
        }
        return rc;
 }
-- 
2.21.GIT