| Message ID | 20220208154000.87070-1-duoming@zju.edu.cn (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 7ec02f5ac8a5be5a3f20611731243dc5e1d9ba10 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | ax25: fix NPD bug in ax25_disconnect | expand |
Hello: This patch was applied to netdev/net.git (master) by David S. Miller <davem@davemloft.net>: On Tue, 8 Feb 2022 23:40:00 +0800 you wrote: > The ax25_disconnect() in ax25_kill_by_device() is not > protected by any locks, thus there is a race condition > between ax25_disconnect() and ax25_destroy_socket(). > when ax25->sk is assigned as NULL by ax25_destroy_socket(), > a NULL pointer dereference bug will occur if site (1) or (2) > dereferences ax25->sk. > > [...] Here is the summary with links: - ax25: fix NPD bug in ax25_disconnect https://git.kernel.org/netdev/net/c/7ec02f5ac8a5 You are awesome, thank you!
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 3e49d28824e..3d87040d1bf 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -92,8 +92,8 @@ static void ax25_kill_by_device(struct net_device *dev) lock_sock(sk); s->ax25_dev = NULL; ax25_dev_put(ax25_dev); - release_sock(sk); ax25_disconnect(s, ENETUNREACH); + release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); /* The entry could have been deleted from the
The ax25_disconnect() in ax25_kill_by_device() is not protected by any locks, thus there is a race condition between ax25_disconnect() and ax25_destroy_socket(). when ax25->sk is assigned as NULL by ax25_destroy_socket(), a NULL pointer dereference bug will occur if site (1) or (2) dereferences ax25->sk. ax25_kill_by_device() | ax25_release() ax25_disconnect() | ax25_destroy_socket() ... | if(ax25->sk != NULL) | ... ... | ax25->sk = NULL; bh_lock_sock(ax25->sk); //(1) | ... ... | bh_unlock_sock(ax25->sk); //(2)| This patch moves ax25_disconnect() into lock_sock(), which can synchronize with ax25_destroy_socket() in ax25_release(). Fail log: =============================================================== BUG: kernel NULL pointer dereference, address: 0000000000000088 ... RIP: 0010:_raw_spin_lock+0x7e/0xd0 ... Call Trace: ax25_disconnect+0xf6/0x220 ax25_device_event+0x187/0x250 raw_notifier_call_chain+0x5e/0x70 dev_close_many+0x17d/0x230 rollback_registered_many+0x1f1/0x950 unregister_netdevice_queue+0x133/0x200 unregister_netdev+0x13/0x20 ... Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- net/ax25/af_ax25.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)