Fix races around the access to ->s_options

Put generic_show_options read access to s_options under rcu_read_lock,
split save_mount_options() into "we are setting it the first time"
(uses in foo_fill_super()) and "we are relacing and freeing the old one",
synchronize_rcu() before kfree() in the latter.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/afs/super.c b/fs/afs/super.c
index 2753f16dd31..76828e5f8a3 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -408,17 +408,17 @@ static int afs_get_sb(struct file_system_type *fs_type,
 			deactivate_locked_super(sb);
 			goto error;
 		}
-		sb->s_options = new_opts;
+		save_mount_options(sb, new_opts);
 		sb->s_flags |= MS_ACTIVE;
 	} else {
 		_debug("reuse");
-		kfree(new_opts);
 		ASSERTCMP(sb->s_flags, &, MS_ACTIVE);
 	}
 
 	simple_set_mnt(mnt, sb);
 	afs_put_volume(params.volume);
 	afs_put_cell(params.cell);
+	kfree(new_opts);
 	_leave(" = 0 [%p]", sb);
 	return 0;