From 15484377f597ca98ee84de87caa13667ea68bb14 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Wed, 3 Sep 2014 21:35:40 +0800 Subject: [PATCH] Btrfs: fix unprotected device list access when getting the fs information When we get the fs information, we forgot to acquire the mutex of device list, it might cause the problem we might access a device that was removed. Fix it by acquiring the device list mutex. Signed-off-by: Miao Xie Signed-off-by: Chris Mason --- fs/btrfs/super.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 3f1f4e2..2375f94 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1696,7 +1696,11 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf) struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv; int ret; - /* holding chunk_muext to avoid allocating new chunks */ + /* + * holding chunk_muext to avoid allocating new chunks, holding + * device_list_mutex to avoid the device being removed + */ + mutex_lock(&fs_info->fs_devices->device_list_mutex); mutex_lock(&fs_info->chunk_mutex); rcu_read_lock(); list_for_each_entry_rcu(found, head, list) { @@ -1737,11 +1741,13 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf) ret = btrfs_calc_avail_data_space(fs_info->tree_root, &total_free_data); if (ret) { mutex_unlock(&fs_info->chunk_mutex); + mutex_unlock(&fs_info->fs_devices->device_list_mutex); return ret; } buf->f_bavail += div_u64(total_free_data, factor); buf->f_bavail = buf->f_bavail >> bits; mutex_unlock(&fs_info->chunk_mutex); + mutex_unlock(&fs_info->fs_devices->device_list_mutex); buf->f_type = BTRFS_SUPER_MAGIC; buf->f_bsize = dentry->d_sb->s_blocksize; -- 2.7.4