From a5a79d00017c9eee68a9bcb40d5dfd6f45f17461 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 2 Mar 2017 16:50:13 +0100 Subject: block: Initialize bd_bdi on inode initialization So far we initialized bd_bdi only in bdget(). That is fine for normal bdev inodes however for the special case of the root inode of blockdev_superblock that function is never called and thus bd_bdi is left uninitialized. As a result bdev_evict_inode() may oops doing bdi_put(root->bd_bdi) on that inode as can be seen when doing: mount -t bdev none /mnt Fix the problem by initializing bd_bdi when first allocating the inode and then reinitializing bd_bdi in bdev_evict_inode(). Thanks to syzkaller team for finding the problem. Reported-by: Dmitry Vyukov Fixes: b1d2dc5659b4 ("block: Make blk_get_backing_dev_info() safe without open bdev") Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- fs/block_dev.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'fs') diff --git a/fs/block_dev.c b/fs/block_dev.c index 77c30f15a02c..2eca00ec4370 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -870,6 +870,7 @@ static void init_once(void *foo) #ifdef CONFIG_SYSFS INIT_LIST_HEAD(&bdev->bd_holder_disks); #endif + bdev->bd_bdi = &noop_backing_dev_info; inode_init_once(&ei->vfs_inode); /* Initialize mutex for freeze. */ mutex_init(&bdev->bd_fsfreeze_mutex); @@ -884,8 +885,10 @@ static void bdev_evict_inode(struct inode *inode) spin_lock(&bdev_lock); list_del_init(&bdev->bd_list); spin_unlock(&bdev_lock); - if (bdev->bd_bdi != &noop_backing_dev_info) + if (bdev->bd_bdi != &noop_backing_dev_info) { bdi_put(bdev->bd_bdi); + bdev->bd_bdi = &noop_backing_dev_info; + } } static const struct super_operations bdev_sops = { @@ -988,7 +991,6 @@ struct block_device *bdget(dev_t dev) bdev->bd_contains = NULL; bdev->bd_super = NULL; bdev->bd_inode = inode; - bdev->bd_bdi = &noop_backing_dev_info; bdev->bd_block_size = i_blocksize(inode); bdev->bd_part_count = 0; bdev->bd_invalidated = 0; -- cgit v1.2.3