Commit that causes the regression:
commit 33ec3e53e7b1869d7851e59e126bdb0fe0bd1982
Author: Jan Kara <[email protected]>
Date: Thu May 16 16:01:27 2019 +0200
loop: Don't change loop device under exclusive opener
Loop module allows calling LOOP_SET_FD while there are other openers of
the loop device. Even exclusive ones. This can lead to weird
consequences such as kernel deadlocks like:
mount_bdev() lo_ioctl()
udf_fill_super()
udf_load_vrs()
sb_set_blocksize() - sets desired block size B
udf_tread()
sb_bread()
__bread_gfp(bdev, block, B)
loop_set_fd()
set_blocksize()
- now __getblk_slow() indefinitely loops because B != bdev
block size
Fix the problem by disallowing LOOP_SET_FD ioctl when there are
exclusive openers of a loop device.
[Deliberately chosen not to CC stable as a user with priviledges to
trigger this race has other means of taking the system down and this
has a potential of breaking some weird userspace setup]
Seems like it solves a race so I'll raise the issue to the commit
author.
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Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1836914
Title:
Doing multiple squashfs (and other loop?) mounts in parallel breaks
Status in linux package in Ubuntu:
Confirmed
Bug description:
On a system running a 5.2 kernel, doing a large number of mounts of
squashfs filesystems in parallel results in the mounts getting out of
sync with their backing devices.
To reproduce,
https://paste.ubuntu.com/p/VCpzGxvy6h/
this breaks people with ~40 snaps (easily achievable given snapd
leaves up to 3 previous revisions of snaps mounted at any given time,
so a person with ~13 snaps that get updated often will hit this
number).
ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: linux-image-5.2.0-8-generic 5.2.0-8.9
ProcVersionSignature: Ubuntu 5.2.0-8.9-generic 5.2.0
Uname: Linux 5.2.0-8-generic x86_64
ApportVersion: 2.20.11-0ubuntu5
Architecture: amd64
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
CurrentDesktop: ubuntu:GNOME
Date: Wed Jul 17 15:11:15 2019
InstallationDate: Installed on 2019-07-17 (0 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Alpha amd64 (20190716)
IwConfig:
ens3 no wireless extensions.
lo no wireless extensions.
Lsusb: Error: command ['lsusb'] failed with exit code 1:
MachineType: QEMU Standard PC (i440FX + PIIX, 1996)
ProcFB: 0 qxldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.2.0-8-generic
root=UUID=9618ebbb-955d-4daf-b29a-37162ec7821a ro quiet splash vt.handoff=7
RelatedPackageVersions:
linux-restricted-modules-5.2.0-8-generic N/A
linux-backports-modules-5.2.0-8-generic N/A
linux-firmware 1.180
RfKill:
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/01/2014
dmi.bios.vendor: SeaBIOS
dmi.bios.version: Ubuntu-1.8.2-1ubuntu1
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-i440fx-xenial
dmi.modalias:
dmi:bvnSeaBIOS:bvrUbuntu-1.8.2-1ubuntu1:bd04/01/2014:svnQEMU:pnStandardPC(i440FX+PIIX,1996):pvrpc-i440fx-xenial:cvnQEMU:ct1:cvrpc-i440fx-xenial:
dmi.product.name: Standard PC (i440FX + PIIX, 1996)
dmi.product.version: pc-i440fx-xenial
dmi.sys.vendor: QEMU
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