[lkml]   [2021]   [Feb]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH v3 3/3] kunit: tool: fix unintentional statefulness in run_kernel()
This is a bug that has been present since the first version of this
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()
>>> 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: 6ebf5866f2e8 ("kunit: tool: add Python wrappers for running KUnit tests")
Signed-off-by: Daniel Latypov <>
Reviewed-by: Brendan Higgins <>
tools/testing/kunit/ | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/kunit/ b/tools/testing/kunit/
index 71b1942f5ccd..6dd3cf6e8efa 100644
--- a/tools/testing/kunit/
+++ b/tools/testing/kunit/
@@ -199,7 +199,9 @@ 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:
 \ /
  Last update: 2021-02-04 23:58    [W:0.050 / U:1.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site