netconsole: fix multiple race conditions

In every netconsole option that can be set through configfs there's a
race when checking for nt->enabled since it can be modified at the same
time. Probably the most damage can be done by store_enabled when racing
with another instance of itself. Fix all the races with one stone by
moving the mutex lock around the ->store call for all options.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 1505dcb..c9a1592 100644 (file)
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -325,9 +325,7 @@ static ssize_t store_enabled(struct netconsole_target *nt,
                return -EINVAL;
        }
 
-       mutex_lock(&nt->mutex);
        if (enabled) {  /* 1 */
-
                /*
                 * Skip netpoll_parse_options() -- all the attributes are
                 * already configured via configfs. Just print them out.
@@ -335,13 +333,10 @@ static ssize_t store_enabled(struct netconsole_target *nt,
                netpoll_print_options(&nt->np);
 
                err = netpoll_setup(&nt->np);
-               if (err) {
-                       mutex_unlock(&nt->mutex);
+               if (err)
                        return err;
-               }
 
                printk(KERN_INFO "netconsole: network logging started\n");
-
        } else {        /* 0 */
                /* We need to disable the netconsole before cleaning it up
                 * otherwise we might end up in write_msg() with
@@ -354,7 +349,6 @@ static ssize_t store_enabled(struct netconsole_target *nt,
        }
 
        nt->enabled = enabled;
-       mutex_unlock(&nt->mutex);
 
        return strnlen(buf, count);
 }
@@ -571,8 +565,10 @@ static ssize_t netconsole_target_attr_store(struct config_item *item,
        struct netconsole_target_attr *na =
                container_of(attr, struct netconsole_target_attr, attr);
 
+       mutex_lock(&nt->mutex);
        if (na->store)
                ret = na->store(nt, buf, count);
+       mutex_unlock(&nt->mutex);
 
        return ret;
 }