When request a none support device operation, there will be no reply. In this case, the len(desc) check will always be true, causing print_field to enter an infinite loop and crash the program. Example reproducer: # ethtool.py -c veth0 To fix this, return immediately if there is no reply. Fixes: f3d07b02b2b8 ("tools: ynl: ethtool testing tool") Signed-off-by: Hangbin Liu --- tools/net/ynl/pyynl/ethtool.py | 3 +++ 1 file changed, 3 insertions(+) diff --git a/tools/net/ynl/pyynl/ethtool.py b/tools/net/ynl/pyynl/ethtool.py index 9b523cbb3568..fd0f6b8d54d1 100755 --- a/tools/net/ynl/pyynl/ethtool.py +++ b/tools/net/ynl/pyynl/ethtool.py @@ -44,6 +44,9 @@ def print_field(reply, *desc): Pretty-print a set of fields from the reply. desc specifies the fields and the optional type (bool/yn). """ + if not reply: + return + if len(desc) == 0: return print_field(reply, *zip(reply.keys(), reply.keys())) -- 2.50.1