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>

1 files changed, 3 insertions, 7 deletions

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 1505dcb950fa..c9a15925a1f7 100644
--- 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;
 }