Bluetooth: ISO: fix use-after-free of listener socket in iso_conn_ready

Overview

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

Bluetooth: ISO: fix use-after-free of listener socket in iso_conn_ready

iso_conn_ready() looks up the BIS listener socket with iso_get_sock(), which takes a reference, and then, without re-checking its state, creates a child socket from it:

parent = iso_get_sock(hdev, ...);
if (!parent)
    return;

lock_sock(parent);
sk = iso_sock_alloc(sock_net(parent), NULL, BTPROTO_ISO, ...);
...
iso_chan_add(conn, sk, parent);
...
release_sock(parent);
sock_put(parent);

If the listener socket is closed concurrently, between iso_get_sock() and lock_sock(), the reference taken by iso_get_sock() may be the last one: the close path drops the link-list reference, and once iso_conn_ready() drops its own reference at the end of the function the socket is freed. The child socket, however, is already linked to the freed parent, and a later disconnect of the child runs iso_chan_del() -> bt_accept_unlink(), which dereferences the dangling parent pointer into the freed accept queue (a use-after-free). The same dangling pointer is also dereferenced through parent->***() in iso_chan_del().

Fix it the same way the connected (non-BIS) path was fixed in commit 0d255e63fcf3 ("Bluetooth: ISO: hold sk properly in iso_conn_ready"): after taking the socket lock, re-check that the parent is still a listening, alive socket, and bail out otherwise.

Affected

• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < 1702f12cf59a1c3b670eb6bb4a4d6fcccf07e3b8
• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < d47b8f8c02a3d3f282693e5a4ff1f6b4b00518de
• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < 2387cd06a2c0b416f05028b02bba1089f54c28d9
• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < 49fd7116f76b860b230843700fb7423ab5331e1f
• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < 03288b7447c9e572f8ab82fc29cfb4ca719ab210
• Linux >= ccf74f2390d60a2f9a75ef496d2564abb478f46a < 560bef609fa5992745929e8d7d458b9d88dd2830
• Linux 6.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.