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abd93c85c8
sco_conn_del() drops a reference it does not own. It takes one transient
reference via sco_conn_hold_unless_zero() and releases it with the
sco_conn_put() that follows sco_sock_hold(); the additional put in the
!sk branch releases a second one:
conn = sco_conn_hold_unless_zero(conn);
...
sk = sco_sock_hold(conn);
sco_conn_unlock(conn);
sco_conn_put(conn);
if (!sk) {
sco_conn_put(conn);
return;
}
When close() races the controller's Disconnection Complete, sco_chan_del()
clears conn->sk and drops the socket's reference while sco_conn_del() is
running. sco_conn_del() then sees sk == NULL, its own put drops the count
to zero and frees the conn, and the second put writes to the freed kref:
BUG: KASAN: slab-use-after-free in sco_conn_put.part.0+0x1a/0x190
Write of size 4 at addr ffff8881099dec74 by task kworker/u17:3/413
Workqueue: hci1 hci_rx_work
Call Trace:
sco_conn_put.part.0+0x1a/0x190
hci_disconn_complete_evt+0x1ee/0x3e0
hci_event_packet+0x54a/0x650
hci_rx_work+0x321/0x3d0
Allocated by task 413:
sco_conn_add+0x72/0x1a0
sco_connect_cfm+0x88/0x670
Freed by task 413:
sco_conn_del.isra.0+0x3f/0xf0
hci_disconn_complete_evt+0x1ee/0x3e0
refcount_t: underflow; use-after-free.
The root cause is that the socket stores the connection without holding a
reference of its own. __sco_chan_add() does:
sco_pi(sk)->conn = conn;
so the socket borrows whatever reference its caller happened to hold, and
the callers paper over that with ad-hoc holds and puts. Give the socket a
counted reference instead: __sco_chan_add() takes one and it is released
together with the channel (sco_chan_del()) and in sco_sock_destruct().
With the socket holding its own reference, sco_conn_del() no longer needs
the extra put and the redundant hold in sco_conn_ready() goes away.
Making the socket own its reference means the connection is now actually
freed on the error paths of sco_connect() where it used to leak, which in
turn runs sco_conn_free() and its hci_conn_drop(conn->hcon). To keep the
hci_conn accounting balanced, make that ownership explicit as well:
sco_conn_add() consumes one hci_conn reference and the sco_conn owns it for
its lifetime. sco_connect() hands over the reference returned by
hci_connect_sco() and no longer drops it on the error paths;
sco_connect_cfm(), which is not given a reference, takes one with
hci_conn_hold() before handing it to sco_conn_add() (and drops it again if
the allocation fails); and the explicit hci_conn_hold() in sco_conn_ready()
is removed. Every reference then has a single, clear owner.
Fixes:
|
||
|---|---|---|
| .. | ||
| 6lowpan | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| atm | ||
| batman-adv | ||
| bluetooth | ||
| bpf | ||
| bridge | ||
| can | ||
| ceph | ||
| core | ||
| dcb | ||
| devlink | ||
| dns_resolver | ||
| dsa | ||
| ethernet | ||
| ethtool | ||
| handshake | ||
| hsr | ||
| ieee802154 | ||
| ife | ||
| ipv4 | ||
| ipv6 | ||
| iucv | ||
| kcm | ||
| key | ||
| l2tp | ||
| l3mdev | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| mac802154 | ||
| mctp | ||
| mpls | ||
| mptcp | ||
| ncsi | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| nfc | ||
| nsh | ||
| openvswitch | ||
| packet | ||
| phonet | ||
| psample | ||
| psp | ||
| qrtr | ||
| rds | ||
| rfkill | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| shaper | ||
| smc | ||
| strparser | ||
| sunrpc | ||
| switchdev | ||
| tipc | ||
| tls | ||
| unix | ||
| vmw_vsock | ||
| wireless | ||
| x25 | ||
| xdp | ||
| xfrm | ||
| compat.c | ||
| devres.c | ||
| Kconfig | ||
| Kconfig.debug | ||
| Makefile | ||
| socket.c | ||
| sysctl_net.c | ||