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

[ Upstream commit 858f1bf65d3d9c00b5e2d8ca87dc79ed88267c98 ]

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>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220521073749.3146892-6-yukuai3@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 ed678037ba6dec75dd0fc43da84e0c47f8e0ed5d..c860a993085535c9af1cf328d8e8348b5a1f271a 100644 (file)
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1814,17 +1814,7 @@ 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;
@@ -1929,8 +1919,19 @@ 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;