I was able to reproduce this with the attached snapd which is essentialls
PR#7999 plus the following patch:
"""
diff --git a/cmd/snap/cmd_auto_import.go b/cmd/snap/cmd_auto_import.go
index 7408371e11..f6b8f1d0d0 100644
--- a/cmd/snap/cmd_auto_import.go
+++ b/cmd/snap/cmd_auto_import.go
@@ -38,7 +38,6 @@ import (
"github.com/snapcore/snapd/i18n"
"github.com/snapcore/snapd/logger"
"github.com/snapcore/snapd/osutil"
- "github.com/snapcore/snapd/release"
)
const autoImportsName = "auto-import.assert"
@@ -264,11 +263,6 @@ func (x *cmdAutoImport) Execute(args []string) error {
return ErrExtraArgs
}
- if release.OnClassic && !x.ForceClassic {
- fmt.Fprintf(Stderr, "auto-import is disabled on classic\n")
- return nil
- }
-
for _, path := range x.Mount {
// udev adds new /dev/loopX devices on the fly when a
// loop mount happens and there is no loop device left.
"""
and then running the following spread test as shell code:
"""
echo "Setup the image as a block device"
# without -P this test will not work, then /dev/loop1p? will be missing
losetup -fP fake.img
losetup -a |grep fake.img|cut -f1 -d: > loop.txt
LOOP="$(cat loop.txt)"
echo "Create an empty partition header"
echo "label: gpt" | sfdisk "$LOOP"
echo "Get the UC20 gadget"
snap download --channel=20/edge pc
unsquashfs -d gadget-dir pc_*.snap
LOOP="$(cat loop.txt)"
echo "Run the snap-bootstrap tool"
/usr/lib/snapd/snap-bootstrap create-partitions --encrypt --mount
--key-file keyfile ./gadget-dir "$LOOP"
"""
** Attachment added: "snapd_1337.2.43.1_amd64.deb"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860231/+attachment/5321900/+files/snapd_1337.2.43.1_amd64.deb
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https://bugs.launchpad.net/bugs/1860231
Title:
5.4.0-11 crash on cryptsetup open
Status in linux package in Ubuntu:
Incomplete
Bug description:
An attempt to run cryptsetup open on a newly created LUKS partition on
Ubuntu Core 20 causes a kernel crash. This happens in 100% of the
attempts on the snapd Core 20 installation test, but on an image
created to reproduce this bug it happens only when certain parameters
are passed to cryptsetup. Both images are built similarly so the
reason for this discrepancy is unknown. The kernel was installed from
pc-kernel_374.snap.
Linux version 5.4.0-11-generic (buildd@lgw01-amd64-021) (gcc version
9.2.1 20200104 (Ubuntu 9.2.1-22ubuntu2)) #14-Ubuntu SMP Thu Jan 9
16:14:26 UTC 2020
Version signature: Ubuntu 5.4.0-11.14-generic 5.4.8
How to reproduce the crash in 3 "easy" steps:
1. Build a Core 20 image using the attached model file:
1.1. Install the ubuntu-image from latest/edge
$ sudo snap install --channel latest/edge ubuntu-image
1.2. Build the image
$ sudo ubuntu-image --image-size=4G ubuntu-core-20-amd64.model
2. Boot the image in kvm
2.1. Install ovmf version 0~20190606.20d2e5a1-2ubuntu1 or newer (the
stock ovmf from bionic may not work)
2.2. Boot the image
$ sudo kvm -snapshot -m 2048 -smp 4 \
-netdev user,id=mynet0,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80 \
-device virtio-net-pci,netdev=mynet0 \
-drive file=pc.img,if=virtio \
-bios /usr/share/OVMF/OVMF_CODE.ms.fd
2.3. In the grub menu, edit the default option to include parameter
"systemd.debug-shell=1" in the kernel command line
2.4. Boot the kernel
3. Crash the kernel
3.1. When the system boots to the "Press enter to configure"
message, press ALT-F9 to enter the debug shell.
3.2. The system should have two partitions in /dev/vda. Create a
third one with fdisk.
3.3. Create a LUKS encrypted partition:
# echo 123|cryptsetup luksFormat -q --type luks2 --key-file - --pbkdf
argon2i --iter-time 1 /dev/vda3
(the system will complain about a missing locking directory,
just ignore it.)
3.4. Open the encrypted device:
# echo 123|cryptsetup open --key-file - /dev/vda name
The Core 20 images contain the following udev rule which causes
the new block device to be mounted automatically. This mount is
what triggers the BUG:
ACTION=="add", SUBSYSTEM=="block", KERNEL!="loop*", KERNEL!="ram*" \
RUN+="/usr/bin/unshare -m /usr/bin/snap auto-import --mount=/dev/%k"
3.5. Read the crash message
The attached screenshots show these steps being executed.
A few notes:
- The backtrace seems very similar to the one reported in bug #1835279,
however that problem was possibly caused by a race between partition creation
and LUKS formatting. This time it doesn't seem to be the case, delays between
commands don't help us here.
- In the test case above using large values of KDF iter-time may prevent the
crash. I successfully opened the device in kernel 5.4.0-9 with --iter-time
larger than 100, but 5.4.0-11 seems to require values closer to 1000.
Regardless of the --iter-time value used, the crash always happen when running
the test in a spread-driven automated environment (same kernel with image built
in the same way, some other variable seems to be disturbing the system).
- All necessary modules are loaded before the LUKS partition creation (i.e.
it doesn't seem to be caused by a race between dm-crypt loading and cryptsetup
luksFormat for example).
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1860231/+subscriptions
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