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nbd: fix max value for 'first_minor'
commitb1a811633f
("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:b1a811633f
("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>
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1 changed files with 3 additions and 3 deletions
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@ -1808,11 +1808,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
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disk->major = NBD_MAJOR;
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/* Too big first_minor can cause duplicate creation of
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* sysfs files/links, since first_minor will be truncated to
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* byte in __device_add_disk().
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* sysfs files/links, since MKDEV() expect that the max bits of
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* first_minor is 20.
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*/
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disk->first_minor = index << part_shift;
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if (disk->first_minor > 0xff) {
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if (disk->first_minor > MINORMASK) {
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err = -EINVAL;
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goto out_free_idr;
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}
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