close the race in nlmsvc_free_block()

we need to grab mutex before the reference counter reaches 0

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index fb1a2be..8d80c99 100644 (file)
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -289,7 +289,6 @@ static void nlmsvc_free_block(struct kref *kref)
        dprintk("lockd: freeing block %p...\n", block);
 
        /* Remove block from file's list of blocks */
-       mutex_lock(&file->f_mutex);
        list_del_init(&block->b_flist);
        mutex_unlock(&file->f_mutex);
 
@@ -303,7 +302,7 @@ static void nlmsvc_free_block(struct kref *kref)
 static void nlmsvc_release_block(struct nlm_block *block)
 {
        if (block != NULL)
-               kref_put(&block->b_count, nlmsvc_free_block);
+               kref_put_mutex(&block->b_count, nlmsvc_free_block, &block->b_file->f_mutex);
 }
 
 /*