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| author | Yu Kuai <yukuai3@huawei.com> | 2021-11-02 04:52:34 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-18 21:17:05 +0300 |
| commit | 795e6b378692d8cf6fd4d1328d8f3e39c36c1e12 (patch) | |
| tree | 1c2a7e98456ab78f3848b12aac5041edec41a83c /drivers/block | |
| parent | f314286463bca5051eb20ba67dbc712959154122 (diff) | |
| download | linux-795e6b378692d8cf6fd4d1328d8f3e39c36c1e12.tar.xz | |
nbd: fix max value for 'first_minor'
[ 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>
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/nbd.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 4f1b591c3a55..0d820c4dec17 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1749,11 +1749,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) disk->major = NBD_MAJOR; /* Too big first_minor can cause duplicate creation of - * sysfs files/links, since first_minor will be truncated to - * byte in __device_add_disk(). + * sysfs files/links, since MKDEV() expect that the max bits of + * first_minor is 20. */ disk->first_minor = index << part_shift; - if (disk->first_minor > 0xff) { + if (disk->first_minor > MINORMASK) { err = -EINVAL; goto out_free_idr; } |