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authorDuoming Zhou <duoming@zju.edu.cn>2022-02-08 18:40:00 +0300
committerDavid S. Miller <davem@davemloft.net>2022-02-09 14:55:02 +0300
commit7ec02f5ac8a5be5a3f20611731243dc5e1d9ba10 (patch)
treee81d40938d51c4a8ed0326df32057ea05c6a7dec /net/ax25
parent676b49366a70ea91997585ba8e4577290f5172a5 (diff)
downloadlinux-7ec02f5ac8a5be5a3f20611731243dc5e1d9ba10.tar.xz
ax25: fix NPD bug in ax25_disconnect
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> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ax25')
-rw-r--r--net/ax25/af_ax25.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 3e49d28824ed..3d87040d1bfc 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -92,8 +92,8 @@ again:
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