5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Breno Leitao <leitao@xxxxxxxxxx>
commit 97d9fba9a812cada5484667a46e14a4c976ca330 upstream.
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>
Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Link: https://patch.msgid.link/20240712143415.1141039-1-leitao@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/netconsole.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -715,6 +715,7 @@ restart:
/* rtnl_lock already held
* we might sleep in __netpoll_cleanup()
*/
+ nt->enabled = false;
spin_unlock_irqrestore(&target_list_lock, flags);
__netpoll_cleanup(&nt->np);
@@ -722,7 +723,6 @@ restart:
spin_lock_irqsave(&target_list_lock, flags);
dev_put(nt->np.dev);
nt->np.dev = NULL;
- nt->enabled = false;
stopped = true;
netconsole_target_put(nt);
goto restart;
