🛡️ CVE-2024-36013 — kernel

Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect()

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect()

Extend a critical section to prevent chan from early freeing.

Also make the l2cap_connect() return type void. Nothing is using the

returned value but it is ugly to return a potentially freed pointer.

Making it void will help with backports because earlier kernels did use

the return value. Now the compile will break for kernels where this

patch is not a complete fix.

Call stack summary:

[use]

l2cap_bredr_sig_cmd

l2cap_connect

┌ mutex_lock(&conn->chan_lock);

│ chan = pchan->ops->new_connection(pchan); <- alloc chan

│ __l2cap_chan_add(conn, chan);

│ l2cap_chan_hold(chan);

│ list_add(&chan->list, &conn->chan_l); ... (1)

└ mutex_unlock(&conn->chan_lock);

chan->conf_state ... (4) <- use after free

[free]

l2cap_conn_del

┌ mutex_lock(&conn->chan_lock);

│ foreach chan in conn->chan_l: ... (2)

│ l2cap_chan_put(chan);

│ l2cap_chan_destroy

│ kfree(chan) ... (3) <- chan freed

└ mutex_unlock(&conn->chan_lock);

==================================================================

BUG: KASAN: slab-use-after-free in instrument_atomic_read

include/linux/instrumented.h:68 [inline]

BUG: KASAN: slab-use-after-free in _test_bit

include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]

BUG: KASAN: slab-use-after-free in l2cap_connect+0xa67/0x11a0

net/bluetooth/l2cap_core.c:4260

Read of size 8 at addr ffff88810bf040a0 by task kworker/u3:1/311