795e6b3786
[ Upstream commit e4c4871a73944353ea23e319de27ef73ce546623 ]
commit b1a811633f73 ("block: nbd: add sanity check for first_minor")
checks that 'first_minor' should not be greater than 0xff, which is
wrong. Whitout the commit, the details that when user pass 0x100000,
it ends up create sysfs dir "/sys/block/43:0" are as follows:
nbd_dev_add
disk->first_minor = index << part_shift
-> default part_shift is 5, first_minor is 0x2000000
device_add_disk
ddev->devt = MKDEV(disk->major, disk->first_minor)
-> (0x2b << 20) | (0x2000000) = 0x2b00000
device_add
device_create_sys_dev_entry
format_dev_t
sprintf(buffer, "%u:%u", MAJOR(dev), MINOR(dev));
-> got 43:0
sysfs_create_link -> /sys/block/43:0
By the way, with the wrong fix, when part_shift is the default value,
only 8 ndb devices can be created since 8 << 5 is greater than 0xff.
Since the max bits for 'first_minor' should be the same as what
MKDEV() does, which is 20. Change the upper bound of 'first_minor'
from 0xff to 0xfffff.
Fixes: b1a811633f73 ("block: nbd: add sanity check for first_minor")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20211102015237.2309763-2-yebin10@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.