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: 2382b15bcc39 ("netconsole: take care of NETDEV_UNREGISTER event")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
---
Changelog:
v2:
* Targeting "net" instead of "net-dev" (Jakub)
v1:
* https://lore.kernel.org/all/20240709144403.544099-4-leitao@xxxxxxxxxx/
drivers/net/netconsole.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index d7070dd4fe73..aa66c923790f 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -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;
--
2.43.0
