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Jan Kara
897366537f
When two blkdev_open() calls race with device removal and recreation,
__blkdev_get() can use looked up gendisk after it is freed:
CPU0 CPU1 CPU2
del_gendisk(disk);
bdev_unhash_inode(inode);
blkdev_open() blkdev_open()
bdev = bd_acquire(inode);
- creates and returns new inode
bdev = bd_acquire(inode);
- returns the same inode
__blkdev_get(devt) __blkdev_get(devt)
disk = get_gendisk(devt);
- got structure of device going away
<finish device removal>
<new device gets
created under the same
device number>
disk = get_gendisk(devt);
- got new device structure
if (!bdev->bd_openers) {
does the first open
}
if (!bdev->bd_openers)
- false
} else {
put_disk_and_module(disk)
- remember this was old device - this was last ref and disk is
now freed
}
disk_unblock_events(disk); -> oops
Fix the problem by making sure we drop reference to disk in
__blkdev_get() only after we are really done with it.
Reported-by: Hou Tao <houtao1@huawei.com>
Tested-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.