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 1CB1051D51C for ; Wed, 30 Sep 2026 18:28:44 +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=1790792925; cv=none; b=XSxYUuN7Nxi/koNfZytMPrIsBmxQSBYG23Tb3WD0CEDpaSnVfMtkeA8EGbenemFDgloCpLxv+nwGiElmAxHGqkByHQ9P/mJSrIkNCQ4lyPUU5BSVijJSxp2CL3oH0n5+3RxAh9ZFn6tMhXyCN/xSO0fdqaXLTxts80S4bP/Ooao= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790792925; c=relaxed/simple; bh=mm3zlNv3SBPVydioYtGlxyfjJ0Xm3BjfE5JATrlZSO8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=l/bTYf6cxXzVix8N2hMAxvaDzOjy7aPx5ABQHucDpizqVeDQyXIogDMb2Aej0/vWXUI3EkOUokwUhFfsqN+sRH7auR70n0AjNTM4jRnSsXHSiLIB1KRekyHb0rQfbpFIiHz3u3t58DAsSTSkE3jwul+15n3QI8lsFEBbRLPUCz0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UjZmzRZ2; 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="UjZmzRZ2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 631391F00898; Wed, 30 Sep 2026 18:28:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790792923; bh=5/2XcPzRnJi13o6PDe9fmNaEUM7lt+2EMF8dPfUuvLM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UjZmzRZ2f6YmGC9pJzYuh9D3ZVXXZI86txDCg8gySQZAH5BGfoo9PGev+gfHieOCO S3D2a0E/gUsnD7h6ZC4yRQUHJZiZT0J8lyWslR1IkymVLlHipLk1a0iDk0X1hx/57v uPP5twZrI38Vw/XMjEMkDcSsR1oULyLbzwkfrUZvvzqpW18nuxfGXn9od5+aH2Czu9 FmFqfFYQe/E9IgyNygSkyH+VNON1Kw1rED31muGiqGdzxSqmWaJUyr04QrkWZjVbdS eUaGDHj38fgE+idTVsZ70F+mGYBx4u3XmdsboY+ULTALZFh9PFhDEIKMzuDii8OaQH cgpBZOmDwhlow== From: Sasha Levin To: stable@vger.kernel.org Cc: Sungwoo Kim , Luiz Augusto von Dentz , Sasha Levin Subject: [PATCH 5.15.y 1/3] Bluetooth: L2CAP: Fix slab-use-after-free in l2cap_connect() Date: Wed, 30 Sep 2026 14:28:39 -0400 Message-ID: <20260930182841.34239-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026092958-cathouse-visiting-7f57@gregkh> References: <2026092958-cathouse-visiting-7f57@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: Sungwoo Kim [ Upstream commit 4d7b41c0e43995b0e992b9f8903109275744b658 ] 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 Fixes: 73ffa904b782 ("Bluetooth: Move conf_{req,rsp} stuff to struct l2cap_chan") Signed-off-by: Sungwoo Kim Signed-off-by: Luiz Augusto von Dentz Stable-dep-of: b5dbb41b212c ("Bluetooth: mgmt: fix race in read_unconf_index_list()") Signed-off-by: Sasha Levin --- net/bluetooth/l2cap_core.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index 34f89f7f993be..0140f82fdc8df 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -4201,13 +4201,12 @@ static inline int l2cap_command_rej(struct l2cap_conn *conn, return 0; } -static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, - struct l2cap_cmd_hdr *cmd, - u8 *data, u8 rsp_code, u8 amp_id) +static void l2cap_connect(struct l2cap_conn *conn, struct l2cap_cmd_hdr *cmd, + u8 *data, u8 rsp_code, u8 amp_id) { struct l2cap_conn_req *req = (struct l2cap_conn_req *) data; struct l2cap_conn_rsp rsp; - struct l2cap_chan *chan = NULL, *pchan; + struct l2cap_chan *chan = NULL, *pchan = NULL; int result, status = L2CAP_CS_NO_INFO; u16 dcid = 0, scid = __le16_to_cpu(req->scid); @@ -4220,7 +4219,7 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, &conn->hcon->dst, ACL_LINK); if (!pchan) { result = L2CAP_CR_BAD_PSM; - goto sendresp; + goto response; } mutex_lock(&conn->chan_lock); @@ -4309,17 +4308,15 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, } response: - l2cap_chan_unlock(pchan); - mutex_unlock(&conn->chan_lock); - l2cap_chan_put(pchan); - -sendresp: rsp.scid = cpu_to_le16(scid); rsp.dcid = cpu_to_le16(dcid); rsp.result = cpu_to_le16(result); rsp.status = cpu_to_le16(status); l2cap_send_cmd(conn, cmd->ident, rsp_code, sizeof(rsp), &rsp); + if (!pchan) + return; + if (result == L2CAP_CR_PEND && status == L2CAP_CS_NO_INFO) { struct l2cap_info_req info; info.type = cpu_to_le16(L2CAP_IT_FEAT_MASK); @@ -4342,7 +4339,9 @@ static struct l2cap_chan *l2cap_connect(struct l2cap_conn *conn, chan->num_conf_req++; } - return chan; + l2cap_chan_unlock(pchan); + mutex_unlock(&conn->chan_lock); + l2cap_chan_put(pchan); } static int l2cap_connect_req(struct l2cap_conn *conn, -- 2.53.0