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net: netconsole: Disable target before netpoll cleanup

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Currently, netconsole cleans up the netpoll structure before disabling
the target. This approach can lead to race conditions, as message
senders (write_ext_msg() and write_msg()) check if the target is
enabled before using netpoll. The sender can validate that the target is
enabled, but, the netpoll might be de-allocated already, causing
undesired behaviours.

This patch reverses the order of operations:
1. Disable the target
2. Clean up the netpoll structure

This change eliminates the potential race condition, ensuring that
no messages are sent through a partially cleaned-up netpoll structure.

Fixes: 2382b15bcc ("netconsole: take care of NETDEV_UNREGISTER event")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20240712143415.1141039-1-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Breno Leitao 2024-07-12 07:34:15 -07:00 committed by Jakub Kicinski
parent d657f5c76c
commit 97d9fba9a8
1 changed files with 1 additions and 1 deletions
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2
drivers/net/netconsole.c
View file

@ -974,6 +974,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
/* rtnl_lock already held
* we might sleep in __netpoll_cleanup()
*/
nt->enabled = false;
spin_unlock_irqrestore(&target_list_lock, flags);
__netpoll_cleanup(&nt->np);
@ -981,7 +982,6 @@ static int netconsole_netdev_event(struct notifier_block *this,
spin_lock_irqsave(&target_list_lock, flags);
netdev_put(nt->np.dev, &nt->np.dev_tracker);
nt->np.dev = NULL;
nt->enabled = false;
stopped = true;
netconsole_target_put(nt);
goto restart;