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Message-Id: <20220418121208.707407249@linuxfoundation.org>
Date: Mon, 18 Apr 2022 14:13:27 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Duoming Zhou <duoming@....edu.cn>,
"David S. Miller" <davem@...emloft.net>,
Ovidiu Panait <ovidiu.panait@...driver.com>
Subject: [PATCH 5.15 187/189] ax25: fix NPD bug in ax25_disconnect
From: Duoming Zhou <duoming@....edu.cn>
commit 7ec02f5ac8a5be5a3f20611731243dc5e1d9ba10 upstream.
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@....edu.cn>
Signed-off-by: David S. Miller <davem@...emloft.net>
[OP: backport to 5.15: adjust context]
Signed-off-by: Ovidiu Panait <ovidiu.panait@...driver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
net/ax25/af_ax25.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -102,8 +102,8 @@ again:
dev_put(ax25_dev->dev);
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
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