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

[Shuvam Pandey]

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 <shuvam...@gmail.com>
---
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
--
2.50.0

[David Gow]

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 <shuvam...@gmail.com>
> ---

Nice catch!

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

Thanks,
-- David