** Description changed: "initramfs unpacking failed: Decoding failed", message appears on boot up. If I "update-initramfs" using gzip instead of lz, then boot up passes without decoding failed message. --- However, we currently believe that the decoding error reported in dmesg is actually harmless and has no impact on usability on the system. Switching from lz4 to gzip compression, simply papers over the warning, without any benefits, and slows down boot. Kernel should be fixed to correctly parse lz4 compressed initrds, or at least lower the warning, to not be user visible as an error. + + [Impact] + + * Decoding failure messages in dmsg with a single lz4 initrd + + * Multiple lz4 compressed initrds cannot be decompressed by kernel, + when loaded by grub + + * Multiple lz4 compressed initrds cannot be decompressed by kernel, + when there is padding between them + + [Test Case] + + * Create empty padding with $ dd if=/dev/zero of=pad4 bs=1 count=4 + + * Create an lz4 compressed initrd with a single test-file in it with + some content. I.e. echo "second-initrd" > test-file, and then pack that + with cpio hewc owned by root & lz4 -l. + + * Create a combined padded initrd of stock initrd, pad4, and the test- + marker initrd created above. + + * Boot above with "break=top" kernel command line. + + * With broken kernels, there should be dmesg error message that + decoding failed, and one will observe that /test-file does not exist in + the shell. + + * With fixed kernel, /test-file in the initrd shell should exist, and + should have the expected content "second-initrd". + + * The alignment and padding in the above test case depends on the size + of the first initrd => if a given padded initrd does not reproduce the + problem, try varying the size of the first initrd or that of the padding + between 0..4. + + + [Where problems could occur] + + * This changes compatible lz4 decompressor in the kernel, which can + also be used by other kernel modules such as cryptography, squashfs, + zram, f2fs, comprssed kernel image, pstore. For example, previously + rejected files with "bogus" length and extra padding may now be + accepted, whereas they were previously getting rejected by the + decompressor. + + * Ideally kernel should switch to the stable lz4 format which has + better specification of end of stream.
** Patch added: "0001-lib-decompress_unlz4.c-correctly-handle-zero-padding.patch" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1835660/+attachment/5440421/+files/0001-lib-decompress_unlz4.c-correctly-handle-zero-padding.patch -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1835660 Title: initramfs unpacking failed To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/1835660/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
