[Bug 240853] Any moderate I/O panics the kernel when MAC_BIBA + multilabel is enabled

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=240853

--- Comment #3 from kayront <realkay at mailbox.org> ---
- Exact FreeBSD version (uname -a)

FreeBSD fbsdtest 12.0-RELEASE-p10 FreeBSD 12.0-RELEASE-p10 GENERIC  amd64

- /var/run/dmesg.boot output (as an attachment)

Will attach.

- Check and confirm that the file system is clean (fsck -fy in single user), or
report back if it is not

/dev/vtbd0p2: FILE SYSTEM CLEAN; SKIPPING CHECKS

- See if you can obtain a kernel panic backtrace [1], and in particular try to
catch the initial "panic message"

It is: softdep_deallocate_dependencies: dangling deps

Funnily (or tragically, I guess) enough with dumps enabled it then proceeds to
panic while writing the crash summary:

Writing crash summary to /var/crash/core.txt.0.
panic: softdep_deallocate_dependencies: dangling deps
cpuid = 0
time = 1569663157
KDB: stack backtrace:
#0 0xffffffff80be78d7 at kdb_backtrace+0x67
#1 0xffffffff80b9b4b3 at vpanic+0x1a3
#2 0xffffffff80b9b303 at panic+0x43
#3 0xffffffff80e979f6 at softdep_deallocate_dependencies+0x76
#4 0xffffffff80c4a27f at brelse+0x16f
#5 0xffffffff80c4e7fd at buf_recycle+0x2ad
#6 0xffffffff80c4ee57 at bufspace_daemon+0xe7
#7 0xffffffff80b5be83 at fork_exit+0x83
#8 0xffffffff8105061e at fork_trampoline+0xe
Uptime: 9s
Dumping 102 out of 472 MB:..16%..32%..47%..63%..78%..94%


- Clarify whether or not the panic is reproducible *without* MAC_BIBA and/or
multilabel enabled (test each combination)

Just tested, and:

root at fbsdtest:~ # kldstat | grep biba
root at fbsdtest:~ # mount|grep label
/dev/vtbd0p2 on / (ufs, local, noatime, journaled soft-updates, multilabel,
acls)
devfs on /dev (devfs, local, multilabel)

Ran a find /, installed some packages, and no problem; this seems to make sense
if you look at the original message, which included:

#17 0xffffffff826abbf6 at biba_vnode_create_extattr+0x126

(this is not present if the module is not loaded)

Without multilabel is how I had the system before and it was fine, so I did not
test again, but let me know if that would add any new useful information.

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