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kunit: tool: fix unintentional statefulness in run_kernel()

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This is a bug that has been present since the first version of this
code.
Using [] as a default parameter is dangerous, since it's mutable.

Example using the REPL:
>>> def bad(param = []):
...     param.append(len(param))
...     print(param)
...
>>> bad()
[0]
>>> bad()
[0, 1]

This wasn't a concern in the past since it would just keep appending the
same values to it.

E.g. before, `args` would just grow in size like:
  [mem=1G', 'console=tty']
  [mem=1G', 'console=tty', mem=1G', 'console=tty']

But with now filter_glob, this is more dangerous, e.g.
  run_kernel(filter_glob='my-test*') # default modified here
  run_kernel()			     # filter_glob still applies here!
That earlier `filter_glob` will affect all subsequent calls that don't
specify `args`.

Note: currently the kunit tool only calls run_kernel() at most once, so
it's not possible to trigger any negative side-effects right now.

Fixes: 6ebf5866f2 ("kunit: tool: add Python wrappers for running KUnit tests")
Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
This commit is contained in:
Daniel Latypov 2021-02-05 16:08:54 -08:00 committed by Shuah Khan
parent d992880b3d
commit 7af29141a3
1 changed files with 3 additions and 1 deletions
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4
tools/testing/kunit/kunit_kernel.py
View file

@ -203,7 +203,9 @@ class LinuxSourceTree(object):
return False
return self.validate_config(build_dir)
def run_kernel(self, args=[], build_dir='', filter_glob='', timeout=None) -> Iterator[str]:
def run_kernel(self, args=None, build_dir='', filter_glob='', timeout=None) -> Iterator[str]:
if not args:
args = []
args.extend(['mem=1G', 'console=tty'])
if filter_glob:
args.append('kunit.filter_glob='+filter_glob)