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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 <dvyukov@google.com>
Fixes: b1d2dc5659 ("block: Make blk_get_backing_dev_info() safe without open bdev")
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jan Kara 2017-03-02 16:50:13 +01:00 committed by Jens Axboe
parent e02898b423
commit a5a79d0001
1 changed files with 4 additions and 2 deletions
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6
fs/block_dev.c
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@ -870,6 +870,7 @@ static void init_once(void *foo)
#ifdef CONFIG_SYSFS #ifdef CONFIG_SYSFS
INIT_LIST_HEAD(&bdev->bd_holder_disks); INIT_LIST_HEAD(&bdev->bd_holder_disks);
#endif #endif
bdev->bd_bdi = &noop_backing_dev_info;
inode_init_once(&ei->vfs_inode); inode_init_once(&ei->vfs_inode);
/* Initialize mutex for freeze. */ /* Initialize mutex for freeze. */
mutex_init(&bdev->bd_fsfreeze_mutex); mutex_init(&bdev->bd_fsfreeze_mutex);
@ -884,8 +885,10 @@ static void bdev_evict_inode(struct inode *inode)
spin_lock(&bdev_lock); spin_lock(&bdev_lock);
list_del_init(&bdev->bd_list); list_del_init(&bdev->bd_list);
spin_unlock(&bdev_lock); 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); bdi_put(bdev->bd_bdi);
bdev->bd_bdi = &noop_backing_dev_info;
}
} }
static const struct super_operations bdev_sops = { static const struct super_operations bdev_sops = {
@ -988,7 +991,6 @@ struct block_device *bdget(dev_t dev)
bdev->bd_contains = NULL; bdev->bd_contains = NULL;
bdev->bd_super = NULL; bdev->bd_super = NULL;
bdev->bd_inode = inode; bdev->bd_inode = inode;
bdev->bd_bdi = &noop_backing_dev_info;
bdev->bd_block_size = i_blocksize(inode); bdev->bd_block_size = i_blocksize(inode);
bdev->bd_part_count = 0; bdev->bd_part_count = 0;
bdev->bd_invalidated = 0; bdev->bd_invalidated = 0;