[PATCH -stable,4.14.y,4.19.y 1/1] ipvs: Improve robustness to the ipvs sysctl

[Julian Anastasov <ja@xxxxxx>]

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>
Acked-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
(cherry picked from commit 1b90af292e71b20d03b837d39406acfbdc5d4b2a)
[Julian: Backport by changing SYSCTL_ZERO/SYSCTL_ONE to zero/one]
Signed-off-by: Julian Anastasov <ja@xxxxxx>
---
 net/netfilter/ipvs/ip_vs_ctl.c | 70 +++++++++++++++++-----------------
 1 file changed, 36 insertions(+), 34 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index ecc16d8c1cc3..4e78c2a6a3ca 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1648,6 +1648,7 @@ static int ip_vs_zero_all(struct netns_ipvs *ipvs)
 #ifdef CONFIG_SYSCTL
 
 static int zero;
+static int one = 1;
 static int three = 3;
 
 static int
@@ -1659,12 +1660,18 @@ 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 */
-                       *valp = val;
+               if (val < 0 || val > 3) {
+                       rc = -EINVAL;
                } else {
+                       *valp = val;
                        update_defense_level(ipvs);
                }
        }
@@ -1678,33 +1685,20 @@ 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));
-       }
-       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;
 }
@@ -1717,12 +1711,18 @@ 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;
 }
@@ -1782,7 +1782,9 @@ static struct ctl_table vs_vars[] = {
                .procname       = "sync_version",
                .maxlen         = sizeof(int),
                .mode           = 0644,
-               .proc_handler   = proc_do_sync_mode,
+               .proc_handler   = proc_dointvec_minmax,
+               .extra1         = &zero,
+               .extra2         = &one,
        },
        {
                .procname       = "sync_ports",
-- 
2.41.0