[PATCH 5.15 255/277] Revert "nbd: fix possible overflow on first_minor in nbd_dev_add()"

From: Greg Kroah-Hartman
Date: Tue Apr 12 2022 - 03:29:24 EST


From: Jens Axboe <axboe@xxxxxxxxx>

commit 7198bfc2017644c6b92d2ecef9b8b8e0363bb5fd upstream.

This reverts commit 6d35d04a9e18990040e87d2bbf72689252669d54.

Both Gabriel and Borislav report that this commit casues a regression
with nbd:

sysfs: cannot create duplicate filename '/dev/block/43:0'

Revert it before 5.18-rc1 and we'll investigage this separately in
due time.

Link: https://lore.kernel.org/all/YkiJTnFOt9bTv6A2@xxxxxxx/
Reported-by: Gabriel L. Somlo <somlo@xxxxxxx>
Reported-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/nbd.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)

--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1744,6 +1744,17 @@ static struct nbd_device *nbd_dev_add(in
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;
@@ -1848,19 +1859,8 @@ static int nbd_genl_connect(struct sk_bu
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;