On 4/21/23 19:32, Sergei Shtepa wrote:
On 4/20/23 21:17, Sergei Shtepa wrote:
Subject:
Re: [PATCH v3 03/11] documentation: Block Devices Snapshots Module
From:
Sergei Shtepa <sergei.shtepa@xxxxxxxxx>
Date:
4/20/23, 21:17
To:
Donald Buczek <buczek@xxxxxxxxxxxxx>, axboe@xxxxxxxxx, hch@xxxxxxxxxxxxx, corbet@xxxxxxx, snitzer@xxxxxxxxxx
CC:
viro@xxxxxxxxxxxxxxxxxx, brauner@xxxxxxxxxx, willy@xxxxxxxxxxxxx, kch@xxxxxxxxxx, martin.petersen@xxxxxxxxxx, vkoul@xxxxxxxxxx, ming.lei@xxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, linux-block@xxxxxxxxxxxxxxx, linux-doc@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx
On 4/20/23 16:44, Donald Buczek wrote:
Subject:
Re: [PATCH v3 03/11] documentation: Block Devices Snapshots Module
From:
Donald Buczek <buczek@xxxxxxxxxxxxx>
Date:
4/20/23, 16:44
To:
Sergei Shtepa <sergei.shtepa@xxxxxxxxx>, axboe@xxxxxxxxx, hch@xxxxxxxxxxxxx, corbet@xxxxxxx, snitzer@xxxxxxxxxx
CC:
viro@xxxxxxxxxxxxxxxxxx, brauner@xxxxxxxxxx, willy@xxxxxxxxxxxxx, kch@xxxxxxxxxx, martin.petersen@xxxxxxxxxx, vkoul@xxxxxxxxxx, ming.lei@xxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, linux-block@xxxxxxxxxxxxxxx, linux-doc@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx
On 4/19/23 21:42, Donald Buczek wrote:
Dear Sergei,
On 4/19/23 15:05, Sergei Shtepa wrote:
[...]
Patches in attach and https://github.com/SergeiShtepa/linux/tree/blksnap-master
Thanks. I can confirm that this fixes the reported problem and I no longer can trigger the UAF. 😄
Tested-Bny: Donald Buczek <buczek@xxxxxxxxxxxxx>
Maybe you can add me to the cc list for v4 as I'm not subscribed to the lists.
Sorry, found another one. Reproducer:
=====
#! /bin/bash
set -xe
modprobe blksnap
test -e /scratch/local/test.dat || fallocate -l 1G /scratch/local/test.dat
s=$(blksnap snapshot_create -d /dev/vdb)
blksnap snapshot_appendstorage -i $s -f /scratch/local/test.dat
blksnap snapshot_take -i $s
s2=$(blksnap snapshot_create -d /dev/vdb)
blksnap snapshot_destroy -i $s2
blksnap snapshot_destroy -i $s
=====
[20382.402921] blksnap-snapshot: Snapshot ff1c54f1-3e8c-4c99-bb26-35e82dc1c9fa was created
[20382.535933] blksnap-image: Create snapshot image device for original device [253:16]
[20382.542405] blksnap-snapshot: Snapshot ff1c54f1-3e8c-4c99-bb26-35e82dc1c9fa was taken successfully
[20382.572564] blksnap-snapshot: Snapshot 4b2d571d-9a24-419d-96c2-8d64a07c4966 was created
[20382.600521] blksnap-snapshot: Destroy snapshot 4b2d571d-9a24-419d-96c2-8d64a07c4966
[20382.602373] blksnap-snapshot: Release snapshot 4b2d571d-9a24-419d-96c2-8d64a07c4966
[20382.722137] blksnap-snapshot: Destroy snapshot ff1c54f1-3e8c-4c99-bb26-35e82dc1c9fa
[20382.724033] blksnap-snapshot: Release snapshot ff1c54f1-3e8c-4c99-bb26-35e82dc1c9fa
[20382.725850] ==================================================================
[20382.727641] BUG: KASAN: wild-memory-access in snapshot_free+0x73/0x170 [blksnap]
[20382.729326] Write of size 8 at addr dead000000000108 by task blksnap/8297
...
Great! Thanks.
There is no protection against re-adding a block device to the snapshot.
I'll take care of it.
Hi!
I think the fix turned out to be quite beautiful.
Now you will get an error "Device or resource busy".
Fix in attach and on github.
Link: https://github.com/SergeiShtepa/linux/commit/43a5d3dd9858f092b734187b6a62ce75acaa47c7
I can confirm, that this fixes the problem.
root@dose:~# blksnap snapshot_create -d /dev/vda -d /dev/vda
fdcd3ee3-a25f-4c2a-93d7-2d951520e938
Operation already in progress
root@dose:~# echo $?
1
Tested-By: Donald Buczek <buczek@xxxxxxxxxxxxx>
Best
Donald
--
Donald Buczek
buczek@xxxxxxxxxxxxx
Tel: +49 30 8413 1433
