Floppy causes processes to hang when trying to access an empty drive

[Buddy Scharfenberg]

I don't think this is a puppet specific bug, it seems to be a somewhat random occurance when something tries to read information about the device /dev/fd* and there is no disk in the drive.

I uncovered this bug in Ubuntu 20.04 when configuring systems with puppet and it appears when facter is gathering facts about the disks on the system and tries to access the fd0 device which doesn't have a disk in it. It encounters an I/O error, and sometimes it does fine while sometimes it gets stuck indefinitely and the only way to kill it is to reboot the system.

The environment is a VMware VM running the 5.4.0-29 kernel.

Here is a relevant excerpt from kern.log>

May 12 22:39:46 r01blspcy kernel: [53528.108033] INFO: task puppet:26247 blocked for more than 1208 seconds.
May 12 22:39:46 r01blspcy kernel: [53528.108805] Not tainted 5.4.0-29-generic #33-Ubuntu
May 12 22:39:46 r01blspcy kernel: [53528.109452] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 12 22:39:46 r01blspcy kernel: [53528.110115] puppet D 0 26247 677 0x00004000
May 12 22:39:46 r01blspcy kernel: [53528.110118] Call Trace:
May 12 22:39:46 r01blspcy kernel: [53528.110125] __schedule+0x2e3/0x740
May 12 22:39:46 r01blspcy kernel: [53528.110127] ? __switch_to_asm+0x40/0x70
May 12 22:39:46 r01blspcy kernel: [53528.110128] ? __switch_to_asm+0x34/0x70
May 12 22:39:46 r01blspcy kernel: [53528.110129] schedule+0x42/0xb0
May 12 22:39:46 r01blspcy kernel: [53528.110131] schedule_timeout+0x203/0x2f0
May 12 22:39:46 r01blspcy kernel: [53528.110132] wait_for_completion+0xb1/0x120
May 12 22:39:46 r01blspcy kernel: [53528.110135] ? wake_up_q+0x70/0x70
May 12 22:39:46 r01blspcy kernel: [53528.110141] __floppy_read_block_0+0x140/0x190 [floppy]
May 12 22:39:46 r01blspcy kernel: [53528.110144] ? floppy_cmos_show+0x30/0x30 [floppy]
May 12 22:39:46 r01blspcy kernel: [53528.110146] floppy_revalidate+0xfc/0x240 [floppy]
May 12 22:39:46 r01blspcy kernel: [53528.110149] check_disk_change+0x62/0x70
May 12 22:39:46 r01blspcy kernel: [53528.110151] floppy_open+0x28e/0x360 [floppy]
May 12 22:39:46 r01blspcy kernel: [53528.110154] ? disk_block_events+0x5c/0x80
May 12 22:39:46 r01blspcy kernel: [53528.110156] __blkdev_get+0xe1/0x550
May 12 22:39:46 r01blspcy kernel: [53528.110157] blkdev_get+0x3d/0x140
May 12 22:39:46 r01blspcy kernel: [53528.110159] ? blkdev_get_by_dev+0x50/0x50
May 12 22:39:46 r01blspcy kernel: [53528.110160] blkdev_open+0x8f/0xa0
May 12 22:39:46 r01blspcy kernel: [53528.110163] do_dentry_open+0x143/0x3a0
May 12 22:39:46 r01blspcy kernel: [53528.110165] vfs_open+0x2d/0x30
May 12 22:39:46 r01blspcy kernel: [53528.110167] do_last+0x194/0x900
May 12 22:39:46 r01blspcy kernel: [53528.110169] path_openat+0x8d/0x290
May 12 22:39:46 r01blspcy kernel: [53528.110171] do_filp_open+0x91/0x100
May 12 22:39:46 r01blspcy kernel: [53528.110174] ? __alloc_fd+0x46/0x150
May 12 22:39:46 r01blspcy kernel: [53528.110175] do_sys_open+0x17e/0x290
May 12 22:39:46 r01blspcy kernel: [53528.110176] __x64_sys_openat+0x20/0x30
May 12 22:39:46 r01blspcy kernel: [53528.110179] do_syscall_64+0x57/0x190
May 12 22:39:46 r01blspcy kernel: [53528.110181] entry_SYSCALL_64_after_hwframe+0x44/0xa9
May 12 22:39:46 r01blspcy kernel: [53528.110182] RIP: 0033:0x7fe17fd75d94
May 12 22:39:46 r01blspcy kernel: [53528.110189] Code: Bad RIP value.
May 12 22:39:46 r01blspcy kernel: [53528.110189] RSP: 002b:00007ffe14425220 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
May 12 22:39:46 r01blspcy kernel: [53528.110191] RAX: ffffffffffffffda RBX: 0000560dcc7ce330 RCX: 00007fe17fd75d94
May 12 22:39:46 r01blspcy kernel: [53528.110192] RDX: 0000000000080000 RSI: 0000560dcc49e4c0 RDI: 00000000ffffff9c
May 12 22:39:46 r01blspcy kernel: [53528.110192] RBP: 0000560dcc49e4c0 R08: 0000000000000000 R09: 00007fe17fe50b80
May 12 22:39:46 r01blspcy kernel: [53528.110193] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000080000
May 12 22:39:46 r01blspcy kernel: [53528.110193] R13: 00007fe17e9ad3c4 R14: 00000000debb66e7 R15: 0000000000000000

[Stig Sandbeck Mathisen (ssm)]

Puppet loads Facter, which has a "partitions" fact and a "disks" fact, both of which may be worth investigating. I'm moving this to the "facter" package.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[andrew bezella (abezella)]

we're testing blacklisting the floppy module as a workaround, per https://tickets.puppetlabs.com/browse/FACT-1922 ([FACT-1922] Log file being spammed with the error: floppy: error -5 while read
ing block 0 - Puppet Tickets)