From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B2990381AEA for ; Fri, 29 May 2026 19:08:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780081697; cv=none; b=tU8EWSdnwLkiNbSSeddMz0VT4ERRRCmFMgEbul7pGsD7MOGLUblMm6rfJUBBL3+IMmJf8tuQRf8BPXihvoO4vJBTQuqcYIOmzgHFRSPjhVWDgZQepXEVbg+hXXGDnDNwhC5Y/tKDljvf2jUNZo0uzCejife8Z2DYllYmbhxduLo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780081697; c=relaxed/simple; bh=ULZxM+/ZMpsSh/9Kd9ZFFEwTgEfc7dYYHXUVKersgEM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=ZmM9u7lpWf5eoPZ0lfqbZun95EDuIAldpQ6lBUsH/5TOeCXYGyTpVUUufSrvs2/WrhMO4aTzyuYGkjSgG8zTQNGipdLn8tYGmHFIJmsAhuAtfQqc8B8phEBELIh3BaPdu/qRzwoJ79sLN0ngaNxnTNQ29WJJ8t0ZwDc8vQXv3ws= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WAAc9LBG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WAAc9LBG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2D251F00893; Fri, 29 May 2026 19:08:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780081695; bh=UxBHuaTNC/YrlXzRiddNqzCbGONDglVSrVAD5Kt+jx4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WAAc9LBGzqePrEptq+aQOw8vYEurlaRDDhI9VB84Bxg32JtlahTe+gGq3U1XYD/+D FXywm89In8XagX4v0F8UOuERg+cCrvQSx3sOi4QkkmHXGzrmWKSQAh8Iy+1SJpqtTZ xA2TckyLHUyZdezT6WK4T64ABB36rlVp2szpmPkhp/+a0vc0FuZUw7T3ZJVt72wX89 EMpqm4jDd9lIH+X5j7BCV9iFD0O7Hmmg/ECZ2r8AYQV/YOd4hO7HG2atsqW6C15UHO +8BD/aP8O8CJ6o8EHMY6sBTpocwNZpy4sUG0iC1RPbay2VuqjkCzxGN5aUTKUtx8kH vXEUO1cavfq4A== From: Sasha Levin To: stable@vger.kernel.org Cc: =?UTF-8?q?Safa=20Karaku=C5=9F?= , Siwei Zhang , Luiz Augusto von Dentz , Sasha Levin Subject: [PATCH 5.15.y] Bluetooth: fix UAF in l2cap_sock_cleanup_listen() vs l2cap_conn_del() Date: Fri, 29 May 2026 15:08:13 -0400 Message-ID: <20260529190813.1682934-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026052807-humped-occultist-d89d@gregkh> References: <2026052807-humped-occultist-d89d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Safa Karakuş [ Upstream commit ab1513597c6cf17cd1ad2a21e3b045421b48e022 ] 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 e83f5e24da741 ("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: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Cc: stable@vger.kernel.org Reported-by: Siwei Zhang Reviewed-by: Siwei Zhang Signed-off-by: Safa Karakuş Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/af_bluetooth.c | 10 +++++++ net/bluetooth/l2cap_sock.c | 51 +++++++++++++++++++++++++++++++----- net/bluetooth/rfcomm/sock.c | 9 ++++++- net/bluetooth/sco.c | 9 ++++++- 4 files changed, 70 insertions(+), 9 deletions(-) diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c index aebef5cf12d48..33d68fc263504 100644 --- a/net/bluetooth/af_bluetooth.c +++ b/net/bluetooth/af_bluetooth.c @@ -259,6 +259,16 @@ 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); return sk; } diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index faaa5e4525c07..be35e3887aa2c 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -366,8 +366,13 @@ 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; @@ -1444,22 +1449,54 @@ 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); } } diff --git a/net/bluetooth/rfcomm/sock.c b/net/bluetooth/rfcomm/sock.c index d1f2c936a8a81..0716f8bf01f36 100644 --- a/net/bluetooth/rfcomm/sock.c +++ b/net/bluetooth/rfcomm/sock.c @@ -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; @@ -503,8 +505,13 @@ static int rfcomm_sock_accept(struct socket *sock, struct socket *newsock, int f } 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; diff --git a/net/bluetooth/sco.c b/net/bluetooth/sco.c index d0ef74c45914c..5901dbbc19181 100644 --- a/net/bluetooth/sco.c +++ b/net/bluetooth/sco.c @@ -394,6 +394,8 @@ 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; @@ -687,8 +689,13 @@ 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; -- 2.53.0