linux-kernel - [PATCH 4.4 01/18] USB: cdc-acm: fix racy tty buffer accesses

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 14 Oct 2021 16:53:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Oliver Neukum <oneukum@...e.com>,
        Johan Hovold <johan@...nel.org>
Subject: [PATCH 4.4 01/18] USB: cdc-acm: fix racy tty buffer accesses

From: Johan Hovold <johan@...nel.org>

commit 65a205e6113506e69a503b61d97efec43fc10fd7 upstream.

A recent change that started reporting break events to the line
discipline caused the tty-buffer insertions to no longer be serialised
by inserting events also from the completion handler for the interrupt
endpoint.

Completion calls for distinct endpoints are not guaranteed to be
serialised. For example, in case a host-controller driver uses
bottom-half completion, the interrupt and bulk-in completion handlers
can end up running in parallel on two CPUs (high-and low-prio tasklets,
respectively) thereby breaking the tty layer's single producer
assumption.

Fix this by holding the read lock also when inserting characters from
the bulk endpoint.

Fixes: 08dff274edda ("cdc-acm: fix BREAK rx code path adding necessary calls")
Cc: stable@...r.kernel.org
Acked-by: Oliver Neukum <oneukum@...e.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
Link: https://lore.kernel.org/r/20210929090937.7410-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/class/cdc-acm.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -407,11 +407,16 @@ static int acm_submit_read_urbs(struct a

 static void acm_process_read_urb(struct acm *acm, struct urb *urb)
 {
+	unsigned long flags;
+
 	if (!urb->actual_length)
 		return;

+	spin_lock_irqsave(&acm->read_lock, flags);
 	tty_insert_flip_string(&acm->port, urb->transfer_buffer,
 			urb->actual_length);
+	spin_unlock_irqrestore(&acm->read_lock, flags);
+
 	tty_flip_buffer_push(&acm->port);
 }