Re: [PATCH] kunit: tool: copy caller args in run_kernel to prevent mutation

[David Gow <david@davidgow.net>]

Le 26/02/2026 à 11:29 PM, Shuvam Pandey a écrit :
> run_kernel() appended KUnit flags directly to the caller-provided args
> list. When exec_tests() calls run_kernel() repeatedly (e.g. with
> --run_isolated), each call mutated the same list, causing later runs
> to inherit stale filter_glob values and duplicate kunit.enable flags.
> 
> Fix this by copying args at the start of run_kernel(). Add a regression
> test that calls run_kernel() twice with the same list and verifies the
> original remains unchanged.
> 
> Fixes: ff9e09a3762f ("kunit: tool: support running each suite/test separately")
> Signed-off-by: Shuvam Pandey <shuvampandey1@gmail.com>
> ---

Nice catch!

Reviewed-by: David Gow <david@davidgow.net>

Thanks,
-- David

>   tools/testing/kunit/kunit_kernel.py    |  6 ++++--
>   tools/testing/kunit/kunit_tool_test.py | 26 ++++++++++++++++++++++++++
>   2 files changed, 30 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/kunit/kunit_kernel.py b/tools/testing/kunit/kunit_kernel.py
> index 260d8d9aa1db..2998e1bc088b 100644
> --- a/tools/testing/kunit/kunit_kernel.py
> +++ b/tools/testing/kunit/kunit_kernel.py
> @@ -346,8 +346,10 @@ class LinuxSourceTree:
>   		return self.validate_config(build_dir)
>   
>   	def run_kernel(self, args: Optional[List[str]]=None, build_dir: str='', filter_glob: str='', filter: str='', filter_action: Optional[str]=None, timeout: Optional[int]=None) -> Iterator[str]:
> -		if not args:
> -			args = []
> +		# Copy to avoid mutating the caller-supplied list. exec_tests() reuses
> +		# the same args across repeated run_kernel() calls (e.g. --run_isolated),
> +		# so appending to the original would accumulate stale flags on each call.
> +		args = list(args) if args else []
>   		if filter_glob:
>   			args.append('kunit.filter_glob=' + filter_glob)
>   		if filter:
> diff --git a/tools/testing/kunit/kunit_tool_test.py b/tools/testing/kunit/kunit_tool_test.py
> index b67408147c1f..f6383884c599 100755
> --- a/tools/testing/kunit/kunit_tool_test.py
> +++ b/tools/testing/kunit/kunit_tool_test.py
> @@ -503,6 +503,32 @@ class LinuxSourceTreeTest(unittest.TestCase):
>   			with open(kunit_kernel.get_outfile_path(build_dir), 'rt') as outfile:
>   				self.assertEqual(outfile.read(), 'hi\nbye\n', msg='Missing some output')
>   
> +	def test_run_kernel_args_not_mutated(self):
> +		"""Verify run_kernel() copies args so callers can reuse them."""
> +		start_calls = []
> +
> +		def fake_start(start_args, unused_build_dir):
> +			start_calls.append(list(start_args))
> +			return subprocess.Popen(['printf', 'KTAP version 1\n'],
> +						text=True, stdout=subprocess.PIPE)
> +
> +		with tempfile.TemporaryDirectory('') as build_dir:
> +			tree = kunit_kernel.LinuxSourceTree(build_dir,
> +					kunitconfig_paths=[os.devnull])
> +			with mock.patch.object(tree._ops, 'start', side_effect=fake_start), \
> +			     mock.patch.object(kunit_kernel.subprocess, 'call'):
> +				kernel_args = ['mem=1G']
> +				for _ in tree.run_kernel(args=kernel_args, build_dir=build_dir,
> +							 filter_glob='suite.test1'):
> +					pass
> +				for _ in tree.run_kernel(args=kernel_args, build_dir=build_dir,
> +							 filter_glob='suite.test2'):
> +					pass
> +				self.assertEqual(kernel_args, ['mem=1G'],
> +					'run_kernel() should not modify caller args')
> +				self.assertIn('kunit.filter_glob=suite.test1', start_calls[0])
> +				self.assertIn('kunit.filter_glob=suite.test2', start_calls[1])
> +
>   	def test_build_reconfig_no_config(self):
>   		with tempfile.TemporaryDirectory('') as build_dir:
>   			with open(kunit_kernel.get_kunitconfig_path(build_dir), 'w') as f:
> 
> base-commit: f4d0ec0aa20d49f09dc01d82894ce80d72de0560