[PATCH net v2] 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.
I delete proc_do_sync_mode and use extra1/2 in table for the
proc_dointvec_minmax call.

Fixes: f73181c8288f ("ipvs: add support for sync threads")
Signed-off-by: Junwei Hu <hujunwei4@xxxxxxxxxx>
---
V1->V2:
- delete proc_do_sync_mode and use proc_dointvec_minmax call.
---
 net/netfilter/ipvs/ip_vs_ctl.c | 69 +++++++++++++++++++++---------------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 060565e..7aed7b0 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1737,12 +1737,18 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
        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);
                }
        }
@@ -1756,33 +1762,20 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
        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));
-       }
-       return rc;
-}
-
-static int
-proc_do_sync_mode(struct ctl_table *table, int write,
-                    void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-       int *valp = table->data;
-       int val = *valp;
-       int rc;
-
-       rc = proc_dointvec(table, write, buffer, lenp, ppos);
-       if (write && (*valp != val)) {
-               if ((*valp < 0) || (*valp > 1)) {
-                       /* Restore the correct value */
-                       *valp = 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;
 }
@@ -1795,12 +1788,18 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
        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;
 }
@@ -1860,7 +1859,9 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
                .procname       = "sync_version",
                .maxlen         = sizeof(int),
                .mode           = 0644,
-               .proc_handler   = proc_do_sync_mode,
+               .proc_handler   = proc_dointvec_minmax,
+               .extra1         = SYSCTL_ZERO,
+               .extra2         = SYSCTL_ONE,
        },
        {
                .procname       = "sync_ports",
-- 
1.7.12.4