nbd: fix possible overflow on 'first_minor' in nbd_dev_add()

[ Upstream commit 6d35d04a9e18990040e87d2bbf72689252669d54 ]

When 'index' is a big numbers, it may become negative which forced
to 'int'. then 'index << part_shift' might overflow to a positive
value that is not greater than '0xfffff', then sysfs might complains
about duplicate creation. Because of this, move the 'index' judgment
to the front will fix it and be better.

Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices")
Fixes: 940c264984fd ("nbd: fix possible overflow for 'first_minor' in nbd_dev_add()")
Signed-off-by: Zhang Wensheng <zhangwensheng5@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220310093224.4002895-1-zhangwensheng5@huawei.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 582b23befb5c45e21888d67d61b87882cca31c5c..1c62262304be6493b1151bf02962db01ccd6e7a6 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1744,17 +1744,6 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs)
        refcount_set(&nbd->refs, 0);
        INIT_LIST_HEAD(&nbd->list);
        disk->major = NBD_MAJOR;
-
-       /* Too big first_minor can cause duplicate creation of
-        * sysfs files/links, since index << part_shift might overflow, or
-        * MKDEV() expect that the max bits of first_minor is 20.
-        */
-       disk->first_minor = index << part_shift;
-       if (disk->first_minor < index || disk->first_minor > MINORMASK) {
-               err = -EINVAL;
-               goto out_free_work;
-       }
-
        disk->minors = 1 << part_shift;
        disk->fops = &nbd_fops;
        disk->private_data = nbd;
@@ -1859,8 +1848,19 @@ static int nbd_genl_connect(struct sk_buff *skb, struct genl_info *info)
        if (!netlink_capable(skb, CAP_SYS_ADMIN))
                return -EPERM;
 
-       if (info->attrs[NBD_ATTR_INDEX])
+       if (info->attrs[NBD_ATTR_INDEX]) {
                index = nla_get_u32(info->attrs[NBD_ATTR_INDEX]);
+
+               /*
+                * Too big first_minor can cause duplicate creation of
+                * sysfs files/links, since index << part_shift might overflow, or
+                * MKDEV() expect that the max bits of first_minor is 20.
+                */
+               if (index < 0 || index > MINORMASK >> part_shift) {
+                       printk(KERN_ERR "nbd: illegal input index %d\n", index);
+                       return -EINVAL;
+               }
+       }
        if (!info->attrs[NBD_ATTR_SOCKETS]) {
                printk(KERN_ERR "nbd: must specify at least one socket\n");
                return -EINVAL;