fix(userspace/libsinsp): avoid possible UB when calling back or front without checking string emptiness

[FedeDP]

What type of PR is this?

/kind bug

Any specific area of the project related to this PR?

/area libsinsp

Does this PR require a change in the driver versions?

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[FedeDP]

This UB was spotted by Falco zig CI: https://github.com/falcosecurity/falco/actions/runs/11106489185?pr=3307
/cc @LucaGuerra @jasondellaluce

/milestone 0.19.0

[LucaGuerra]

Thank you!

[FedeDP]

In both fixes, if m_name is empty i return "/"; perhaps it is better to just return the empty string?

[FedeDP]

Decided together with @jasondellaluce to just return an empty string in these cases.

[FedeDP]

/hold
per #2088 (comment)

[github-actions]

Perf diff from master - unit tests

    12.03%     -2.69%  [.] sinsp_parser::reset
     5.77%     -1.25%  [.] next
     2.50%     +0.55%  [.] sinsp_thread_manager::find_thread
     1.82%     -0.54%  [.] std::_Sp_counted_base<(__gnu_cxx::_Lock_policy)2>::_M_release
     1.14%     -0.53%  [.] std::vector<sinsp_evt_param, std::allocator<sinsp_evt_param> >::emplace_back<sinsp_evt*, unsigned int&, char const*, unsigned long&>
     0.62%     +0.52%  [.] scap_event_encode_params_v
     0.78%     -0.49%  [.] sinsp_fdtable::sinsp_fdtable
     0.78%     -0.49%  [.] libsinsp::runc::match_container_id
     0.55%     +0.47%  [.] sinsp_utils::find_longest_matching_evt_param
     7.07%     +0.45%  [.] sinsp::next

Heap diff from master - unit tests

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Heap diff from master - scap file

peak heap memory consumption: 0B
peak RSS (including heaptrack overhead): 0B
total memory leaked: 0B

Benchmarks diff from master

Comparing gbench_data.json to /root/actions-runner/_work/libs/libs/build/gbench_data.json
Benchmark                                                         Time             CPU      Time Old      Time New       CPU Old       CPU New
----------------------------------------------------------------------------------------------------------------------------------------------
BM_sinsp_split_mean                                            +0.0627         +0.0627           144           153           144           153
BM_sinsp_split_median                                          +0.0737         +0.0737           143           153           143           153
BM_sinsp_split_stddev                                          -0.5464         -0.5462             3             1             3             1
BM_sinsp_split_cv                                              -0.5731         -0.5730             0             0             0             0
BM_sinsp_concatenate_paths_relative_path_mean                  +0.0853         +0.0853            56            61            56            61
BM_sinsp_concatenate_paths_relative_path_median                +0.0887         +0.0888            56            61            56            61
BM_sinsp_concatenate_paths_relative_path_stddev                +0.4784         +0.4787             0             0             0             0
BM_sinsp_concatenate_paths_relative_path_cv                    +0.3622         +0.3624             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_mean                     +0.0566         +0.0566            23            25            23            25
BM_sinsp_concatenate_paths_empty_path_median                   +0.0527         +0.0527            23            25            23            25
BM_sinsp_concatenate_paths_empty_path_stddev                   +3.2203         +3.2248             0             0             0             0
BM_sinsp_concatenate_paths_empty_path_cv                       +2.9941         +2.9984             0             0             0             0
BM_sinsp_concatenate_paths_absolute_path_mean                  +0.1270         +0.1269            56            63            56            63
BM_sinsp_concatenate_paths_absolute_path_median                +0.1297         +0.1297            55            63            55            63
BM_sinsp_concatenate_paths_absolute_path_stddev                +2.2972         +2.2966             0             1             0             1
BM_sinsp_concatenate_paths_absolute_path_cv                    +1.9257         +1.9252             0             0             0             0
BM_sinsp_split_container_image_mean                            +0.0101         +0.0100           392           396           392           396
BM_sinsp_split_container_image_median                          +0.0059         +0.0059           392           395           392           395
BM_sinsp_split_container_image_stddev                          +0.9591         +0.9563             2             4             2             4
BM_sinsp_split_container_image_cv                              +0.9396         +0.9368             0             0             0             0

[FedeDP]

/unhold

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 73.58%. Comparing base (8baec4b) to head (8a0b548).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
userspace/libsinsp/sinsp_filtercheck_fdlist.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2088      +/-   ##
==========================================
- Coverage   73.58%   73.58%   -0.01%     
==========================================
  Files         253      253              
  Lines       31869    31869              
  Branches     5650     5644       -6     
==========================================
- Hits        23452    23451       -1     
+ Misses       8408     8393      -15     
- Partials        9       25      +16     

Flag	Coverage Δ
libsinsp	73.58% <66.66%> (-0.01%)	⬇️

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[jasondellaluce]

/approve

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: FedeDP, jasondellaluce

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