linux-kernel - [PATCH net 0/2] netconsole: Fix userdata race condition

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Message-Id: <20251020-netconsole-fix-race-v1-0-b775be30ee8a@gmail.com>
Date: Mon, 20 Oct 2025 14:22:33 -0700
From: Gustavo Luiz Duarte <gustavold@...il.com>
To: Breno Leitao <leitao@...ian.org>, Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Shuah Khan <shuah@...nel.org>, Matthew Wood <thepacketgeek@...il.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, Gustavo Luiz Duarte <gustavold@...il.com>
Subject: [PATCH net 0/2] netconsole: Fix userdata race condition

This series fixes a race condition in netconsole's userdata handling
where concurrent message transmission could read partially updated
userdata fields, resulting in corrupted netconsole output.

The first patch adds a selftest that reproduces the race condition by
continuously sending messages while rapidly changing userdata values,
detecting any torn reads in the output.

The second patch fixes the issue by ensuring update_userdata() holds
the target_list_lock while updating both extradata_complete and
userdata_length, preventing readers from seeing inconsistent state.

This targets net tree as it fixes a bug introduced in commit df03f830d099
("net: netconsole: cache userdata formatted string in netconsole_target").

Signed-off-by: Gustavo Luiz Duarte <gustavold@...il.com>
---
Gustavo Luiz Duarte (2):
      selftests: netconsole: Add race condition test for userdata corruption
      netconsole: Fix race condition in between reader and writer of userdata

 drivers/net/netconsole.c                           |  5 ++
 .../selftests/drivers/net/netcons_race_userdata.sh | 87 ++++++++++++++++++++++
 2 files changed, 92 insertions(+)
---
base-commit: ffff5c8fc2af2218a3332b3d5b97654599d50cde
change-id: 20251020-netconsole-fix-race-f465f37b57ea

Best regards,
-- 
Gustavo Luiz Duarte <gustavold@...il.com>