[PATCH] s390: z/VM monitor stream.

From: Martin Schwidefsky <schwidefsky@de.ibm.com>

z/VM monitor stream changes:
 - Correct sysctl vs. module ref-counting.

diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
index 6f9ab94bf1fda94e63eaec7f5eb40971ee8a02ae..2d7efbf4fffcaf5241d662a851fb31e7e35efca3 100644 (file)
--- a/arch/s390/appldata/appldata_base.c
+++ b/arch/s390/appldata/appldata_base.c
@@ -372,31 +372,57 @@ static int
 appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
                           void *buffer, size_t *lenp)
 {
-       struct appldata_ops *ops;
-       int rc, len;
+       struct appldata_ops *ops = NULL, *tmp_ops;
+       int rc, len, found;
        char buf[2];
+       struct list_head *lh;
 
+       found = 0;
+       spin_lock_bh(&appldata_ops_lock);
+       list_for_each(lh, &appldata_ops_list) {
+               tmp_ops = list_entry(lh, struct appldata_ops, list);
+               if (&tmp_ops->ctl_table[2] == ctl) {
+                       found = 1;
+               }
+       }
+       if (!found) {
+               spin_unlock_bh(&appldata_ops_lock);
+               return -ENODEV;
+       }
        ops = ctl->data;
+       if (!try_module_get(ops->owner)) {      // protect this function
+               spin_unlock_bh(&appldata_ops_lock);
+               return -ENODEV;
+       }
+       spin_unlock_bh(&appldata_ops_lock);
+
        if (!*lenp || filp->f_pos) {
                *lenp = 0;
+               module_put(ops->owner);
                return 0;
        }
        if (!write) {
                len = sprintf(buf, ops->active ? "1\n" : "0\n");
                if (len > *lenp)
                        len = *lenp;
-               if (copy_to_user(buffer, buf, len))
+               if (copy_to_user(buffer, buf, len)) {
+                       module_put(ops->owner);
                        return -EFAULT;
+               }
                goto out;
        }
        len = *lenp;
-       if (copy_from_user(buf, buffer, len > sizeof(buf) ? sizeof(buf) : len))
+       if (copy_from_user(buf, buffer,
+                          len > sizeof(buf) ? sizeof(buf) : len)) {
+               module_put(ops->owner);
                return -EFAULT;
+       }
 
        spin_lock_bh(&appldata_ops_lock);
        if ((buf[0] == '1') && (ops->active == 0)) {
-               if (!try_module_get(ops->owner)) {
+               if (!try_module_get(ops->owner)) {      // protect tasklet
                        spin_unlock_bh(&appldata_ops_lock);
+                       module_put(ops->owner);
                        return -ENODEV;
                }
                ops->active = 1;
@@ -430,6 +456,7 @@ appldata_generic_handler(ctl_table *ctl, int write, struct file *filp,
 out:
        *lenp = len;
        filp->f_pos += len;
+       module_put(ops->owner);
        return 0;
 }
 
@@ -511,7 +538,6 @@ int appldata_register_ops(struct appldata_ops *ops)
        ops->ctl_table[3].ctl_name = 0;
 
        ops->sysctl_header = register_sysctl_table(ops->ctl_table,1);
-       ops->ctl_table[2].de->owner = ops->owner;
 
        P_INFO("%s-ops registered!\n", ops->name);
        return 0;
@@ -525,10 +551,11 @@ int appldata_register_ops(struct appldata_ops *ops)
 void appldata_unregister_ops(struct appldata_ops *ops)
 {
        spin_lock_bh(&appldata_ops_lock);
-       list_del(&ops->list);
-       spin_unlock_bh(&appldata_ops_lock);
        unregister_sysctl_table(ops->sysctl_header);
+       list_del(&ops->list);
        kfree(ops->ctl_table);
+       ops->ctl_table = NULL;
+       spin_unlock_bh(&appldata_ops_lock);
        P_INFO("%s-ops unregistered!\n", ops->name);
 }
 /********************** module-ops management <END> **************************/