Messages in this thread | | | Date | Tue, 18 Apr 2023 16:48:00 +0200 | Subject | Re: [PATCH v3 03/11] documentation: Block Devices Snapshots Module | From | Donald Buczek <> |
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On 4/18/23 12:31, Sergei Shtepa wrote: > > > On 4/14/23 14:34, Sergei Shtepa wrote: >> Subject: >> Re: [PATCH v3 03/11] documentation: Block Devices Snapshots Module >> From: >> Sergei Shtepa <sergei.shtepa@veeam.com> >> Date: >> 4/14/23, 14:34 >> >> To: >> Donald Buczek <buczek@molgen.mpg.de>, axboe@kernel.dk, hch@infradead.org, corbet@lwn.net, snitzer@kernel.org >> CC: >> viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, kch@nvidia.com, martin.petersen@oracle.com, vkoul@kernel.org, ming.lei@redhat.com, gregkh@linuxfoundation.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org >> >> >> >> On 4/12/23 21:38, Donald Buczek wrote: >>> Subject: >>> Re: [PATCH v3 03/11] documentation: Block Devices Snapshots Module >>> From: >>> Donald Buczek <buczek@molgen.mpg.de> >>> Date: >>> 4/12/23, 21:38 >>> >>> To: >>> Sergei Shtepa <sergei.shtepa@veeam.com>, axboe@kernel.dk, hch@infradead.org, corbet@lwn.net, snitzer@kernel.org >>> CC: >>> viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, kch@nvidia.com, martin.petersen@oracle.com, vkoul@kernel.org, ming.lei@redhat.com, gregkh@linuxfoundation.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org >>> >>> >>> I think, you can trigger all kind of user-after-free when userspace deletes a snapshot image or the snapshot image and the tracker while the disk device snapshot image is kept alive (mounted or just opened) and doing I/O. >>> >>> Here is what I did to provoke that: >>> >>> root@dose:~# s=$(blksnap snapshot_create -d /dev/vdb) >>> root@dose:~# blksnap snapshot_appendstorage -i $s -f /scratch/local/test.dat >>> device path: '/dev/block/253:2' >>> allocate range: ofs=11264624 cnt=2097152 >>> root@dose:~# blksnap snapshot_take -i $s >>> root@dose:~# mount /dev/blksnap-image_253\:16 /mnt >>> root@dose:~# dd if=/dev/zero of=/mnt/x.x & >>> [1] 2514 >>> root@dose:~# blksnap snapshot_destroy -i $s >>> dd: writing to '/mnt/x.x': No space left on device >>> 1996041+0 records in >>> 1996040+0 records out >>> 1021972480 bytes (1.0 GB, 975 MiB) copied, 8.48923 s, 120 MB/s >>> [1]+ Exit 1 dd if=/dev/zero of=/mnt/x.x >>> >> Thanks! >> I am very glad that the blksnap tool turned out to be useful in the review. >> This snapshot deletion scenario is not the most typical, but of course it is >> quite possible. >> I will need to solve this problem and add such a scenario to the test suite. >> > > Hi! > > I have redesign the logic of ownership of the diff_area structure. > See patch in attach or commit. > Link: https://github.com/SergeiShtepa/linux/commit/7e927c381dcd2b2293be8315897a224d111b6f88 > A test script for such a scenario has been added. > Link: https://github.com/veeam/blksnap/commit/fd0559dfedf094901d08bbf185fed288f0156433 > > I will be glad of any feedback.
Great, Thanks!
However, there are two leftover calls to diff_area_free() with its old prototype:
CC [M] drivers/block/blksnap/diff_area.o drivers/block/blksnap/diff_area.c: In function ‘diff_area_new’: drivers/block/blksnap/diff_area.c:283:18: error: passing argument 1 of ‘diff_area_free’ from incompatible pointer type [-Werror=incompatible-pointer-types] 283 | diff_area_free(diff_area); | ^~~~~~~~~ | | | struct diff_area * drivers/block/blksnap/diff_area.c:110:34: note: expected ‘struct kref *’ but argument is of type ‘struct diff_area *’ 110 | void diff_area_free(struct kref *kref) | ~~~~~~~~~~~~~^~~~ cc1: some warnings being treated as errors make[4]: *** [scripts/Makefile.build:252: drivers/block/blksnap/diff_area.o] Error 1 make[3]: *** [scripts/Makefile.build:494: drivers/block/blksnap] Error 2 make[2]: *** [scripts/Makefile.build:494: drivers/block] Error 2 make[1]: *** [scripts/Makefile.build:494: drivers] Error 2 make: *** [Makefile:2025: .] Error 2
The other one:
buczek@dose:/scratch/local/linux (blksnap-test)$ make drivers/block/blksnap/tracker.o CALL scripts/checksyscalls.sh DESCEND objtool INSTALL libsubcmd_headers CC [M] drivers/block/blksnap/tracker.o drivers/block/blksnap/tracker.c: In function ‘tracker_free’: drivers/block/blksnap/tracker.c:26:25: error: passing argument 1 of ‘diff_area_free’ from incompatible pointer type [-Werror=incompatible-pointer-types] 26 | diff_area_free(tracker->diff_area); | ~~~~~~~^~~~~~~~~~~ | | | struct diff_area * In file included from drivers/block/blksnap/tracker.c:12: drivers/block/blksnap/diff_area.h:116:34: note: expected ‘struct kref *’ but argument is of type ‘struct diff_area *’ 116 | void diff_area_free(struct kref *kref); | ~~~~~~~~~~~~~^~~~ cc1: some warnings being treated as errors make[4]: *** [scripts/Makefile.build:252: drivers/block/blksnap/tracker.o] Error 1 make[3]: *** [scripts/Makefile.build:494: drivers/block/blksnap] Error 2 make[2]: *** [scripts/Makefile.build:494: drivers/block] Error 2 make[1]: *** [scripts/Makefile.build:494: drivers] Error 2 make: *** [Makefile:2025: .] Error 2
Am I missing something?
Best Donald
-- Donald Buczek buczek@molgen.mpg.de Tel: +49 30 8413 1433
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