The verification of the Stable Release Update for qemu has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.
-- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1422307 Title: qemu-nbd corrupts files Status in QEMU: Fix Released Status in qemu package in Ubuntu: Fix Released Status in qemu source package in Trusty: Fix Released Bug description: [Impact] A race condition in the VDI block driver of Qemu leads to image (and thus file system) corruption under certain circumstances. This makes Qemu tools usage for VDI formatted images particularly dangerous (qemu-img, qemu-nbd). The bug fix introduces locks to prevent such race condition. [Test Case] A simple test case was provided in comment #5 (https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1422307/comments/5): $ ./qemu-img create -f vdi test.vdi 2G Formatting 'test.vdi', fmt=vdi size=2147483648 static=off $ ./qemu-img create -f raw test.raw 2G Formatting 'test.raw', fmt=raw size=2147483648 $ x86_64-softmmu/qemu-system-x86_64 -enable-kvm -drive if=virtio,file=blkverify:test.raw:test.vdi,format=raw -drive if=virtio,file=data.img,format=raw,format=raw -cdrom ~/tmp/arch.iso -m 512 -boot d blkverify: read sector_num=810976 nb_sectors=256 contents mismatch in sector 811008 Operations in the guest: $ dd if=/dev/vdb of=/dev/vda $ dd if=/dev/vda of=/dev/null [Regression Potential] In case of bugs affecting the way locks are used, deadlocks could be a regression, but they would only affect VDI images. Original bug report: Dear all, On Trusty, in certain situations, try to copy files over a qemu-nbd mounted file system leads to write errors (and thus, file corruption). Here is the last example I tried: -> virtual disk is a VDI disk -> It has only one partition, in FAT Here is my mount process: # modprobe nbd max_part=63 # qemu-nbd -c /dev/nbd0 "virtual_disk.vdi" # partprobe /dev/nbd0 # mount /dev/nbd0p1 /tmp/mnt/ Partition is properly mounted at that point: /dev/nbd0p1 on /tmp/mnt type vfat (rw) Now, when I copy a file (rather big, ~28MB): # cp file_to_copy /tmp/mnt/ ; sync # md5sum /tmp/mnt/file_to_copy 2efc9f32e4267782b11d63d2f128a363 /tmp/mnt/file_to_copy # umount /tmp/mnt # mount /dev/nbd0p1 /tmp/mnt/ # md5sum /tmp/mnt/file_to_copy 42b0a3bf73f704d03ce301716d7654de /tmp/mnt/file_to_copy The first hash was obviously the right one. On a previous attempt I did, I spotted thanks to vbindiff that parts of the file were just filed with 0s instead of actual data. It will randomly work after several attempts to write. Version information: # qemu-nbd --version qemu-nbd version 0.0.1 Written by Anthony Liguori. Cheers, To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1422307/+subscriptions
