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authorPavel Skripkin2021-08-12 12:15:01 +0300
committerJens Axboe2021-08-16 10:56:33 -0600
commitb1a811633f7321cf1ae2bb76a66805b7720e44c9 (patch)
tree48a1a23c5fb4a7cd233322535a1c71019d0529f2 /drivers/block
parent9ea9b9c48387edc101d56349492ad9c0492ff78d (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>
Diffstat (limited to 'drivers/block')
-rw-r--r--drivers/block/nbd.c10
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;