diff options
| author | Pavel Skripkin <paskripkin@gmail.com> | 2021-08-12 12:15:01 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-09-15 09:47:29 +0200 |
| commit | b3fa499d72a0db612f12645265a36751955c0037 (patch) | |
| tree | fc436d7333913db2a93229c73b036ac9b3bc1aef /drivers/block | |
| parent | c60a31db3990a144adc95df1feed9f7ebba6cd27 (diff) | |
block: nbd: add sanity check for first_minor
[ Upstream commit b1a811633f7321cf1ae2bb76a66805b7720e44c9 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/block')
| -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 25e81b1a59a5..bc3ab98855cf 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1744,7 +1744,17 @@ static int nbd_dev_add(int index) refcount_set(&nbd->refs, 1); 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->fops = &nbd_fops; disk->private_data = nbd; sprintf(disk->disk_name, "nbd%d", index); |