OpenZFS 9424 - ztest failure: "unprotected error in call to Lua API

[behlendorf]

Description

Ztest failed with the following crash.

::status

debugging core file of ztest (64-bit) from clone-dc-slave-280-bc7947b1.dcenter
file: /usr/bin/amd64/ztest
initial argv: /usr/bin/amd64/ztest
threading model: raw lwps
status: process terminated by SIGABRT (Abort), pid=2150 uid=1025 code=-1
panic message: failure for thread 0xfffffd7fff112a40, thread-id 1: unprotected error in call to Lua API (Invalid
value type 'function' for key 'error')

::stack

libc.so.1`_lwp_kill+0xa()
libc.so.1`_assfail+0x182(fffffd7fffdfe8d0, 0, 0)
libc.so.1`assfail+0x19(fffffd7fffdfe8d0, 0, 0)
libzpool.so.1`vpanic+0x3d(fffffd7ffaa58c20, fffffd7fffdfeb00)
0xfffffd7ffaa28146()
0xfffffd7ffaa0a109()
libzpool.so.1`luaD_throw+0x86(3011a48, 2)
0xfffffd7ffa9350d3()
0xfffffd7ffa93e3f1()
libzpool.so.1`zcp_lua_to_nvlist+0x33(3011a48, 1, 2686470, fffffd7ffaa2e2c3)
libzpool.so.1`zcp_convert_return_values+0xa4(3011a48, 2686470, fffffd7ffaa2e2c3, fffffd7fffdfedd0)
libzpool.so.1`zcp_pool_error+0x59(fffffd7fffdfedd0, 1e0f450)
libzpool.so.1`zcp_eval+0x6f8(1e0f450, fffffd7ffaa483f8, 1, 0, 6400000, 1d33b30)
libzpool.so.1`dsl_destroy_snapshots_nvl+0x12c(2786b60, 0, 484750)
libzpool.so.1`dsl_destroy_snapshot+0x4f(fffffd7fffdfef70, 0)
ztest_dsl_dataset_cleanup+0xea(fffffd7fffdff4c0, 1)
ztest_dataset_destroy+0x53(1)
ztest_run+0x59f(fffffd7fff0e0498)
main+0x7ff(1, fffffd7fffdffa88)
_start+0x6c()

The problem is that zcp_convert_return_values() assumes that there's
exactly one value on the stack, but that isn't always true. It ends up
putting the wrong thing on the stack which is then consumed by
zcp_convert_return values, which either adds the wrong message to the
nvlist, or blows up.

The fix is to make sure that callers of zcp_convert_return_values()
clear the stack before pushing their error message, and
zcp_convert_return_values() should VERIFY that the stack is the expected
size.

Motivation and Context

OpenZFS-issue: https://www.illumos.org/issues/9424
OpenZFS-commit: openzfs/openzfs@eb7e57429

How Has This Been Tested

Locally ran the ZTS channel_program and lua_core test groups.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.
• Change has been approved by a ZFS on Linux member.

[codecov]

Codecov Report

Merging #7696 into master will decrease coverage by 0.23%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master    #7696      +/-   ##
==========================================
- Coverage   78.26%   78.02%   -0.24%     
==========================================
  Files         368      368              
  Lines      111831   111834       +3     
==========================================
- Hits        87525    87261     -264     
- Misses      24306    24573     +267

Flag	Coverage Δ
#kernel	78.71% <66.66%> (-0.07%)	⬇️
#user	66.97% <33.33%> (-0.36%)	⬇️

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