5.4-stable review patch. If anyone has any objections, please let me know.
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From: Breno Leitao leitao@debian.org
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@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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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;