From 7b1485bab9c49b0d3811d72beb0de60c7b8b337d Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 15 Dec 2014 12:56:59 +1100 Subject: [PATCH] md/raid5: use ->lock to protect accessing raid5 sysfs attributes. It is important that mddev->private isn't freed while a sysfs attribute function is accessing it. So use mddev->lock to protect the setting of ->private to NULL, and take that lock when checking ->private for NULL and de-referencing it in the sysfs access functions. This only applies to the read ('show') side of access. Write access will be handled separately. Signed-off-by: NeilBrown --- drivers/md/raid5.c | 44 ++++++++++++++++++++++++++++---------------- 1 file changed, 28 insertions(+), 16 deletions(-) diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index dab908b..d5b8017 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -5354,11 +5354,14 @@ static void raid5d(struct md_thread *thread) static ssize_t raid5_show_stripe_cache_size(struct mddev *mddev, char *page) { - struct r5conf *conf = mddev->private; + struct r5conf *conf; + int ret = 0; + spin_lock(&mddev->lock); + conf = mddev->private; if (conf) - return sprintf(page, "%d\n", conf->max_nr_stripes); - else - return 0; + ret = sprintf(page, "%d\n", conf->max_nr_stripes); + spin_unlock(&mddev->lock); + return ret; } int @@ -5422,11 +5425,14 @@ raid5_stripecache_size = __ATTR(stripe_cache_size, S_IRUGO | S_IWUSR, static ssize_t raid5_show_preread_threshold(struct mddev *mddev, char *page) { - struct r5conf *conf = mddev->private; + struct r5conf *conf; + int ret = 0; + spin_lock(&mddev->lock); + conf = mddev->private; if (conf) - return sprintf(page, "%d\n", conf->bypass_threshold); - else - return 0; + ret = sprintf(page, "%d\n", conf->bypass_threshold); + spin_unlock(&mddev->lock); + return ret; } static ssize_t @@ -5456,11 +5462,14 @@ raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold, static ssize_t raid5_show_skip_copy(struct mddev *mddev, char *page) { - struct r5conf *conf = mddev->private; + struct r5conf *conf; + int ret = 0; + spin_lock(&mddev->lock); + conf = mddev->private; if (conf) - return sprintf(page, "%d\n", conf->skip_copy); - else - return 0; + ret = sprintf(page, "%d\n", conf->skip_copy); + spin_unlock(&mddev->lock); + return ret; } static ssize_t @@ -5512,11 +5521,14 @@ raid5_stripecache_active = __ATTR_RO(stripe_cache_active); static ssize_t raid5_show_group_thread_cnt(struct mddev *mddev, char *page) { - struct r5conf *conf = mddev->private; + struct r5conf *conf; + int ret = 0; + spin_lock(&mddev->lock); + conf = mddev->private; if (conf) - return sprintf(page, "%d\n", conf->worker_cnt_per_group); - else - return 0; + ret = sprintf(page, "%d\n", conf->worker_cnt_per_group); + spin_unlock(&mddev->lock); + return ret; } static int alloc_thread_groups(struct r5conf *conf, int cnt, -- 2.7.4