github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-26 08:02:27 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del()

Browse Source 
bt_accept_dequeue() unlinks a not-yet-accepted child from the parent
accept queue and release_sock()s it before returning, so the returned
sk has no caller reference and is unlocked.

l2cap_sock_cleanup_listen() walks these children on listening-socket
close.  A concurrent HCI disconnect drives hci_rx_work ->
l2cap_conn_del() which runs l2cap_chan_del() + l2cap_sock_kill() and
frees the child sk and its l2cap_chan; cleanup_listen() then uses both:

  BUG: KASAN: slab-use-after-free in l2cap_sock_kill
    l2cap_sock_kill / l2cap_sock_cleanup_listen / __x64_sys_close
  Freed by: l2cap_conn_del -> l2cap_sock_close_cb -> l2cap_sock_kill

This is distinct from the two fixes already in this area: commit
e83f5e24da ("Bluetooth: serialize accept_q access") serialises the
accept_q list/poll and takes temporary refs inside bt_accept_dequeue(),
and CVE-2025-39860 serialises the userspace close()/accept() race by
calling cleanup_listen() under lock_sock() in l2cap_sock_release().
Neither covers l2cap_conn_del() running from hci_rx_work, so this UAF
still reproduces on current bluetooth/master.

Take the reference at the source: bt_accept_dequeue() does sock_hold()
while sk is still locked, before release_sock(); callers sock_put().
cleanup_listen() pins the chan with l2cap_chan_hold_unless_zero() under
a brief child sk lock (serialising vs l2cap_sock_teardown_cb()), drops
it before l2cap_chan_lock(), and skips a duplicate l2cap_sock_kill() on
SOCK_DEAD.  conn->lock is not taken here: cleanup_listen() runs under
the parent sk lock and that would invert
conn->lock -> chan->lock -> sk_lock (lockdep).

KASAN/SMP: an unprivileged listen/close vs HCI-disconnect race produced
12 use-after-free reports per run before this change; 0, and no lockdep
report, over 1600+ raced iterations after it on bluetooth/master.

Fixes: 15f02b9105 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Cc: stable@vger.kernel.org
Reported-by: Siwei Zhang <oss@fourdim.xyz>
Reviewed-by: Siwei Zhang <oss@fourdim.xyz>
Signed-off-by: Safa Karakuş <safa.karakus@secunnix.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Safa Karakuş 2026-05-16 21:15:04 +03:00 committed by Luiz Augusto von Dentz
parent c1bb9336ae
commit ab1513597c
5 changed files with 78 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
net/bluetooth/af_bluetooth.c
View File

@ -340,6 +340,16 @@ struct sock *bt_accept_dequeue(struct sock *parent, struct socket *newsock)
if (newsock)
sock_graft(sk, newsock);
/* Hand the caller a reference taken while sk is
* still locked. bt_accept_unlink() just dropped
* the accept-queue reference; without this hold a
* concurrent teardown (e.g. l2cap_conn_del() ->
* l2cap_sock_kill()) could free sk between
* release_sock() and the caller using it. Every
* caller drops this with sock_put() when done.
*/
sock_hold(sk);
release_sock(sk);
if (next)
sock_put(next);

9
net/bluetooth/iso.c
View File

@ -751,6 +751,8 @@ static void iso_sock_cleanup_listen(struct sock *parent)
while ((sk = bt_accept_dequeue(parent, NULL))) {
iso_sock_close(sk);
iso_sock_kill(sk);
/* Drop the reference handed back by bt_accept_dequeue(). */
sock_put(sk);
}
/* If listening socket has a hcon, properly disconnect it */
@ -1356,8 +1358,13 @@ static int iso_sock_accept(struct socket *sock, struct socket *newsock,
}
ch = bt_accept_dequeue(sk, newsock);
if (ch)
if (ch) {
/* Drop the bridging ref from bt_accept_dequeue();
* the grafted socket keeps ch alive from here.
*/
sock_put(ch);
break;
}
if (!timeo) {
err = -EAGAIN;

51
net/bluetooth/l2cap_sock.c
View File

@ -349,8 +349,13 @@ static int l2cap_sock_accept(struct socket *sock, struct socket *newsock,
}
nsk = bt_accept_dequeue(sk, newsock);
if (nsk)
if (nsk) {
/* Drop the bridging ref from bt_accept_dequeue();
* the grafted socket keeps nsk alive from here.
*/
sock_put(nsk);
break;
}
if (!timeo) {
err = -EAGAIN;
@ -1475,22 +1480,54 @@ static void l2cap_sock_cleanup_listen(struct sock *parent)
BT_DBG("parent %p state %s", parent,
state_to_string(parent->sk_state));
/* Close not yet accepted channels */
/* Close not yet accepted channels.
*
* bt_accept_dequeue() now returns sk with an extra reference held
* (taken while sk was still locked) so a concurrent l2cap_conn_del()
* -> l2cap_sock_kill() cannot free sk under us.
*
* cleanup_listen() runs under the parent sk lock, so unlike
* l2cap_sock_shutdown() we must NOT take conn->lock here: that would
* establish sk_lock -> conn->lock and invert the established
* conn->lock -> chan->lock -> sk_lock order (lockdep deadlock).
*
* Instead, briefly take the child sk lock to fetch and pin its chan.
* l2cap_conn_del() reaches the chan free only via
* l2cap_chan_del() -> l2cap_sock_teardown_cb(), which itself takes
* the child sk lock; holding it across l2cap_chan_hold_unless_zero()
* therefore guarantees the chan cannot be freed while we read and
* pin it (hold_unless_zero() additionally skips a chan already past
* its last reference). We then drop the sk lock before taking
* chan->lock, so sk and chan locks are never held together.
*/
while ((sk = bt_accept_dequeue(parent, NULL))) {
struct l2cap_chan *chan = l2cap_pi(sk)->chan;
struct l2cap_chan *chan;
lock_sock_nested(sk, L2CAP_NESTING_NORMAL);
chan = l2cap_chan_hold_unless_zero(l2cap_pi(sk)->chan);
release_sock(sk);
if (!chan) {
/* l2cap_conn_del() already tearing this child down */
sock_put(sk);
continue;
}
BT_DBG("child chan %p state %s", chan,
state_to_string(chan->state));
l2cap_chan_hold(chan);
l2cap_chan_lock(chan);
__clear_chan_timer(chan);
l2cap_chan_close(chan, ECONNRESET);
l2cap_sock_kill(sk);
/* l2cap_conn_del() may already have killed this socket
* (it sets SOCK_DEAD); skip the duplicate to avoid a
* double sock_put()/l2cap_chan_put().
*/
if (!sock_flag(sk, SOCK_DEAD))
l2cap_sock_kill(sk);
l2cap_chan_unlock(chan);
l2cap_chan_put(chan);
sock_put(sk);
}
}

9
net/bluetooth/rfcomm/sock.c
View File

@ -180,6 +180,8 @@ static void rfcomm_sock_cleanup_listen(struct sock *parent)
while ((sk = bt_accept_dequeue(parent, NULL))) {
rfcomm_sock_close(sk);
rfcomm_sock_kill(sk);
/* Drop the reference handed back by bt_accept_dequeue(). */
sock_put(sk);
}
parent->sk_state = BT_CLOSED;
@ -497,8 +499,13 @@ static int rfcomm_sock_accept(struct socket *sock, struct socket *newsock,
}
nsk = bt_accept_dequeue(sk, newsock);
if (nsk)
if (nsk) {
/* Drop the bridging ref from bt_accept_dequeue();
* the grafted socket keeps nsk alive from here.
*/
sock_put(nsk);
break;
}
if (!timeo) {
err = -EAGAIN;

9
net/bluetooth/sco.c
View File

@ -502,6 +502,8 @@ static void sco_sock_cleanup_listen(struct sock *parent)
while ((sk = bt_accept_dequeue(parent, NULL))) {
sco_sock_close(sk);
sco_sock_kill(sk);
/* Drop the reference handed back by bt_accept_dequeue(). */
sock_put(sk);
}
parent->sk_state = BT_CLOSED;
@ -765,8 +767,13 @@ static int sco_sock_accept(struct socket *sock, struct socket *newsock,
}
ch = bt_accept_dequeue(sk, newsock);
if (ch)
if (ch) {
/* Drop the bridging ref from bt_accept_dequeue();
* the grafted socket keeps ch alive from here.
*/
sock_put(ch);
break;
}
if (!timeo) {
err = -EAGAIN;