From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793211081; b=xwNCW1Lyp6pYkt9P7s7NB9HMUX+3/B9DT9sisMYro/rV+223XAVp0FuPUrRvx9k6i/5M iUOaIvbauVZBwKqBfzSs2V6sX/OqitKE3wx/G0HO22JgqdN48QMhgNlfNWJzsG2CXGPnK VyQb94dRZTIdOX7rRfnGcdI1GpQbQbz/5VV39RDUbICXGzB2vKTLv+icJ7+CAbHQwMToV lVKylnE5urZJMeh7rR4FZj+Rne1F4I2nb2HeleOqhJmMjWgbP8Xl31Bb0lppQS9K5Q9eW s+WXw5SBgNnR4AgPlPnlUtvG2wbrr0GE9IoDrIr6/WySSM5wWP9IAjll6es8dsMmTvg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793211081; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=lS/yp9L3FpyhcBlpSI1I5zcUDiiZHgF5opJZkyOCLvc=; b=GbonIko2dQ2xWqIiZYq85+nIesQzxmgAHjAEM7BVH2YiZ3/yvRCEwVoZBPIZ5g7je/E0 fndTq+/5wXq39Xns3nMCCZd+sINFHpQQhpz9+3O+tqQuB7PkJvVTT99SVTCj21pGcuR/2 nzz2cOqg55MvQwiLRlkMUiP2xbuzg+cl1jJZA5W59Mw4/hoYwclnTJH6KFQ6o+AD6Lnsw uzzZdYcexV92FwuZvcds8zkl2VjqlzNSfVj6Fbe20c4GXl5ccmo11C6QuJ06A6FvkO4N1 N6+sPo+QU1wKjohcUjjz40VAc1kBCdQ5bJzl0SJUjsKuAUKrNInju2TpfF5uxCa96vw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=1REm5Mr8; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E01C260A380A; Wed, 28 Oct 2026 18:11:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=1REm5Mr8 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C6F81F01825; Wed, 28 Oct 2026 18:11:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793211080; bh=lS/yp9L3FpyhcBlpSI1I5zcUDiiZHgF5opJZkyOCLvc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1REm5Mr8JHPjH1gQ/DTUZs7cnEZBPbkPlEJvNF2XzxGuMOTLZv+tse+xMWRalBvGZ mN3Odf4HvOdsEhJ0BUpFM5ptIKVFkxPDUxYMzI/Yxfd+0+egKfv7QFwMaFwPRr3XAe G+RN2Aoip5A1IKmXN+42BwJOAFFLgfkD2R2FCtoc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chengfeng Ye , Luiz Augusto von Dentz Subject: [PATCH 5.15 225/571] Bluetooth: RFCOMM: Fix initial port reference race Date: Wed, 28 Oct 2026 17:56:12 +0100 Message-ID: <20261028170013.340568866@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170008.009143722@linuxfoundation.org> References: <20261028170008.009143722@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chengfeng Ye commit 2d696c1ed3468dcb62578a3911e687110d463520 upstream. For RFCOMM_RELEASE_ONHUP devices, rfcomm_tty_install() and __rfcomm_release_dev() both use RFCOMM_TTY_OWNED to decide who drops the initial tty_port reference. The release path tests the bit separately from the install path setting it, so both can drop that reference. The synchronous hangup does not prevent this race: port->tty is not assigned until tty_port_open(), after installation. The following interleaving is possible: 1. Install and release each obtain a reference with rfcomm_dev_get(). 2. Release observes RFCOMM_TTY_OWNED clear. 3. Install sets RFCOMM_TTY_OWNED and drops the initial reference. 4. Release drops the same initial reference again. 5. TTY cleanup drops its reference and frees the device. 6. Release performs its final tty_port_put() on the freed port. KASAN reported: BUG: KASAN: slab-use-after-free in tty_port_put+0x22/0x190 Write of size 4 at addr ffff8881001d3d5c by task poc/92 Call Trace: tty_port_put+0x22/0x190 rfcomm_dev_ioctl+0x1d4/0x1930 sock_do_ioctl+0x110/0x260 sock_ioctl+0x380/0x590 __x64_sys_ioctl+0x134/0x1c0 Allocated by task 88: rfcomm_dev_ioctl+0x8f6/0x1930 sock_do_ioctl+0x110/0x260 sock_ioctl+0x380/0x590 __x64_sys_ioctl+0x134/0x1c0 Freed by task 65: kfree+0x131/0x3c0 rfcomm_dev_destruct+0x23b/0x2f0 release_one_tty+0xc1/0x370 process_one_work+0x661/0x1090 Use test_and_set_bit() in both paths so that only the caller that changes RFCOMM_TTY_OWNED from clear to set drops the initial reference. Each path keeps its own lookup reference until release or TTY cleanup, preserving the existing callback ordering and error handling. Fixes: 80ea73378af4 ("Bluetooth: Fix unreleased rfcomm_dev reference") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Chengfeng Ye Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Greg Kroah-Hartman --- net/bluetooth/rfcomm/tty.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) --- a/net/bluetooth/rfcomm/tty.c +++ b/net/bluetooth/rfcomm/tty.c @@ -471,7 +471,7 @@ static int __rfcomm_release_dev(void __u tty_kref_put(tty); } - if (!test_bit(RFCOMM_TTY_OWNED, &dev->status)) + if (!test_and_set_bit(RFCOMM_TTY_OWNED, &dev->status)) tty_port_put(&dev->port); tty_port_put(&dev->port); @@ -736,10 +736,9 @@ static int rfcomm_tty_install(struct tty * when the last process closes the tty. The behaviour is expected by * userspace. */ - if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags)) { - set_bit(RFCOMM_TTY_OWNED, &dev->status); + if (test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags) && + !test_and_set_bit(RFCOMM_TTY_OWNED, &dev->status)) tty_port_put(&dev->port); - } return 0; }