netdev - [PATCH net] tools: ynl: avoid print

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Message-ID: <20251024125853.102916-1-liuhangbin@gmail.com>
Date: Fri, 24 Oct 2025 12:58:53 +0000
From: Hangbin Liu <liuhangbin@...il.com>
To: netdev@...r.kernel.org
Cc: Donald Hunter <donald.hunter@...il.com>,
	Jakub Kicinski <kuba@...nel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Jan Stancek <jstancek@...hat.com>,
	"Matthieu Baerts (NGI0)" <matttbe@...nel.org>,
	Asbjørn Sloth Tønnesen <ast@...erby.net>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCH net] tools: ynl: avoid print_field when there is no reply

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 <liuhangbin@...il.com>
---
 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