diff options
| author | Pavel Skripkin | 2021-08-12 12:15:01 +0300 |
|---|---|---|
| committer | Jens Axboe | 2021-08-16 10:56:33 -0600 |
| commit | b1a811633f7321cf1ae2bb76a66805b7720e44c9 (patch) | |
| tree | 48a1a23c5fb4a7cd233322535a1c71019d0529f2 | |
| parent | 9ea9b9c48387edc101d56349492ad9c0492ff78d (diff) | |
block: nbd: add sanity check for first_minor
Syzbot hit WARNING in internal_create_group(). The problem was in
too big disk->first_minor.
disk->first_minor is initialized by value, which comes from userspace
and there wasn't any sanity checks about value correctness. It can cause
duplicate creation of sysfs files/links, because disk->first_minor will
be passed to MKDEV() which causes truncation to byte. Since maximum
minor value is 0xff, let's check if first_minor is correct minor number.
NOTE: the root case of the reported warning was in wrong error handling
in register_disk(), but we can avoid passing knowingly wrong values to
sysfs API, because sysfs error messages can confuse users. For example:
user passed 1048576 as index, but sysfs complains about duplicate
creation of /dev/block/43:0. It's not obvious how 1048576 becomes 0.
Log and reproducer for above example can be found on syzkaller bug
report page.
Link: https://syzkaller.appspot.com/bug?id=03c2ae9146416edf811958d5fd7acfab75b143d1
Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices")
Reported-by: syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/block/nbd.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 0fe82626bf70..379032a64a7c 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1750,7 +1750,17 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) refcount_set(&nbd->refs, refs); INIT_LIST_HEAD(&nbd->list); 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(). + */ disk->first_minor = index << part_shift; + if (disk->first_minor > 0xff) { + err = -EINVAL; + goto out_free_idr; + } + disk->minors = 1 << part_shift; disk->fops = &nbd_fops; disk->private_data = nbd; |