From ee17fc8005287d2d6ca7cab6e814e5043d773735 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Tue, 26 Apr 2016 16:22:06 +0200 Subject: [PATCH] btrfs: sysfs: protect reading label by lock If the label setting ioctl races with sysfs label handler, we could get mixed result in the output, part old part new. We should either get the old or new label. The chances to hit this race are low. Signed-off-by: David Sterba --- fs/btrfs/sysfs.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c index 3d14618ce54b..4879656bda3c 100644 --- a/fs/btrfs/sysfs.c +++ b/fs/btrfs/sysfs.c @@ -367,7 +367,13 @@ static ssize_t btrfs_label_show(struct kobject *kobj, { struct btrfs_fs_info *fs_info = to_fs_info(kobj); char *label = fs_info->super_copy->label; - return snprintf(buf, PAGE_SIZE, label[0] ? "%s\n" : "%s", label); + ssize_t ret; + + spin_lock(&fs_info->super_lock); + ret = snprintf(buf, PAGE_SIZE, label[0] ? "%s\n" : "%s", label); + spin_unlock(&fs_info->super_lock); + + return ret; } static ssize_t btrfs_label_store(struct kobject *kobj, -- 2.30.2