]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/commit
nbd: fix max value for 'first_minor'
authorYu Kuai <yukuai3@huawei.com>
Tue, 2 Nov 2021 01:52:34 +0000 (09:52 +0800)
committerAndrea Righi <andrea.righi@canonical.com>
Tue, 4 Jan 2022 08:48:35 +0000 (09:48 +0100)
commit87178c3a0390c72097202338d07735ecba927033
tree95a82ce6b28c5f92884a339013c9245826265202
parent03873e092df73d3f83914bb2c76e44761baf25f9
nbd: fix max value for 'first_minor'

BugLink: https://bugs.launchpad.net/bugs/1951822
[ 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>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
drivers/block/nbd.c