Patch "nbd: fix possible overflow on 'first_minor' in nbd_dev_add()" has been added to the 5.18-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 5.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nbd-fix-possible-overflow-on-first_minor-in-nbd_dev_.patch
and it can be found in the queue-5.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit f1280e3d5d577eb76fe377c28c4942f8f973c52d
Author: Zhang Wensheng <zhangwensheng5@xxxxxxxxxx>
Date:   Sat May 21 15:37:48 2022 +0800

    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@xxxxxxxxxx>
    Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
    Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220521073749.3146892-6-yukuai3@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index ed678037ba6d..c860a9930855 100644
--- 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;