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 66C103FC5CD; Mon, 7 Sep 2026 06:55:09 +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=1788764110; cv=none; b=DNO0eLoiYbJuSYY+o+IPRcWKQvX4El5JiqrCpHz5OdbsIE5eEyJNinE0ekrRuHzoL69j8WzrXp1AG7Iu09SDIpw5+/8lMk2XD1RFD9Vb7H1rDi18jF2VLQVGeVEPfm8T/CMLpLnyrSaV0mFuayxOlFE3Qe1cadOo7eqR5eWJVgw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788764110; c=relaxed/simple; bh=FDd9iNROPo2O6FFUpxCZ/QST69zsS6w6Lv2RZJ7NhuI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Q+hWmJhk+LmAGtje4EVogSiO69ur7j7SzkOQjxHWNfT60tB9eMZN4kiWQgNmhc9znSNi8wdjY2sOtnhZfveZe6RG5dxuzXpO9MSbDdM6rlTbE1zu5nUL2evqyoVvWSsNtQ2+ESNhvlqplj2jLnR70DwgWwDw4NK8gtMQyO6DTLE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PLBjP0hr; 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="PLBjP0hr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 332011F00A3A; Mon, 7 Sep 2026 06:55:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788764109; bh=z/odk7UzIyLnh0EQGkgHHAaaVYkrwkV+zN1HVD25i4g=; h=From:To:Cc:Subject:Date; b=PLBjP0hrEhrQylxE8HkDg1ifceeh/601zofBojTkXVN3CPhnd2+y8vceDDHIu8kKH Hko0T8hbdKLieq2gBJQVUE+Xc0YvYGfsBW7TaR3jd6ZfrOFmzqgRdv/qNOFFd7fRxP KpORkQZGbAL1eBHFWmjLALwGQu1qzT72yTAfL7eeFgDzgOriZjh5wwd0MmCVk3JT7S SVY0u3bqtW9kt0xPdfFwGV7XA5KarDpvKsmh6DSxgJ3jZBk/F/ITjh4RftkW/acCAF iK9ffTOpum+onQjS1GzYvU5vaHopIWNN85snIcvMdgu5pl5+m+WX39kICHfcFisE4U SEfstFRbyyfOg== Received: from johan by xi.lan with local (Exim 4.99.4) (envelope-from ) id 1x3TFz-00000000QHY-02hU; Mon, 07 Sep 2026 08:55:07 +0200 From: Johan Hovold To: Oliver Neukum , Greg Kroah-Hartman Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Johan Hovold , stable@vger.kernel.org, Oliver Neukum Subject: [PATCH] USB: cdc-acm: fix racy TIOCMIWAIT implementation Date: Mon, 7 Sep 2026 08:55:01 +0200 Message-ID: <20260907065501.101013-1-johan@kernel.org> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The wakeup condition needs to be checked after adding the task to the waitqueue and updating the task state to avoid missing a racing modem status update or disconnect. Fixes: 5a6a62bdb925 ("cdc-acm: add TIOCMIWAIT") Cc: stable@vger.kernel.org # 3.14 Cc: Oliver Neukum Signed-off-by: Johan Hovold --- drivers/usb/class/cdc-acm.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index 7bc5329fa3ed..00c250515e83 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -1027,7 +1027,10 @@ static int wait_serial_change(struct acm *acm, unsigned long arg) DECLARE_WAITQUEUE(wait, current); struct async_icount old, new; - do { + add_wait_queue(&acm->wioctl, &wait); + for (;;) { + set_current_state(TASK_INTERRUPTIBLE); + spin_lock_irq(&acm->read_lock); old = acm->oldcount; new = acm->iocount; @@ -1044,22 +1047,20 @@ static int wait_serial_change(struct acm *acm, unsigned long arg) old.rng != new.rng) break; - add_wait_queue(&acm->wioctl, &wait); - set_current_state(TASK_INTERRUPTIBLE); - schedule(); - remove_wait_queue(&acm->wioctl, &wait); if (acm->disconnected) { - if (arg & TIOCM_CD) - break; - else - rv = -ENODEV; - } else { - if (signal_pending(current)) - rv = -ERESTARTSYS; + rv = -ENODEV; + break; } - } while (!rv); - + schedule(); + + if (signal_pending(current)) { + rv = -ERESTARTSYS; + break; + } + } + __set_current_state(TASK_RUNNING); + remove_wait_queue(&acm->wioctl, &wait); return rv; } -- 2.55.0