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authorDuoming Zhou <duoming@zju.edu.cn>2022-03-08 16:12:23 +0800
committerDavid S. Miller <davem@davemloft.net>2022-03-09 12:45:02 +0000
commit71171ac8eb34ce7fe6b3267dce27c313ab3cb3ac (patch)
treefb7c10dd2acfaf035b19cd8fdd828e75658e286c /net/ax25/af_ax25.c
parentc9ffa3e2bc451816ce0295e40063514fabf2bd36 (diff)
ax25: Fix NULL pointer dereference in ax25_kill_by_device
When two ax25 devices attempted to establish connection, the requester use ax25_create(), ax25_bind() and ax25_connect() to initiate connection. The receiver use ax25_rcv() to accept connection and use ax25_create_cb() in ax25_rcv() to create ax25_cb, but the ax25_cb->sk is NULL. When the receiver is detaching, a NULL pointer dereference bug caused by sock_hold(sk) in ax25_kill_by_device() will happen. The corresponding fail log is shown below: =============================================================== BUG: KASAN: null-ptr-deref in ax25_device_event+0xfd/0x290 Call Trace: ... ax25_device_event+0xfd/0x290 raw_notifier_call_chain+0x5e/0x70 dev_close_many+0x174/0x220 unregister_netdevice_many+0x1f7/0xa60 unregister_netdevice_queue+0x12f/0x170 unregister_netdev+0x13/0x20 mkiss_close+0xcd/0x140 tty_ldisc_release+0xc0/0x220 tty_release_struct+0x17/0xa0 tty_release+0x62d/0x670 ... This patch add condition check in ax25_kill_by_device(). If s->sk is NULL, it will goto if branch to kill device. Fixes: 4e0f718daf97 ("ax25: improve the incomplete fix to avoid UAF and NPD bugs") Reported-by: Thomas Osterried <thomas@osterried.de> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ax25/af_ax25.c')
-rw-r--r--net/ax25/af_ax25.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index d53cbb4e2503..6bd097180772 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -87,6 +87,13 @@ again:
ax25_for_each(s, &ax25_list) {
if (s->ax25_dev == ax25_dev) {
sk = s->sk;
+ if (!sk) {
+ spin_unlock_bh(&ax25_list_lock);
+ s->ax25_dev = NULL;
+ ax25_disconnect(s, ENETUNREACH);
+ spin_lock_bh(&ax25_list_lock);
+ goto again;
+ }
sock_hold(sk);
spin_unlock_bh(&ax25_list_lock);
lock_sock(sk);