linux-kernel - [PATCH 1/3] input: evdev: only allow reading events if a full packet is present

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Message-Id: <1324058826-12891-1-git-send-email-dima@android.com>
Date:	Fri, 16 Dec 2011 10:07:04 -0800
From:	Dima Zavin <dima@...roid.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dima Zavin <dima@...roid.com>,
	Jeff Brown <jeffbrown@...roid.com>
Subject: [PATCH 1/3] input: evdev: only allow reading events if a full packet is present

Without this, it was possible for the reader to get ahead of packet_head.
If the the input device generated a partial packet *right* after the
reader got ahead, then we can get into a situation where the device is
marked readable but read always returns 0 until the next packet is
finished (i.e a SYN is generated by the input driver).

This situation can also happen if we overflow the buffer while a reader
is trying to read an event out.

Cc: Jeff Brown <jeffbrown@...roid.com>
Signed-off-by: Dima Zavin <dima@...roid.com>
---
 drivers/input/evdev.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 4cf2534..03344b3 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -369,7 +369,7 @@ static int evdev_fetch_next_event(struct evdev_client *client,
 
 	spin_lock_irq(&client->buffer_lock);
 
-	have_event = client->head != client->tail;
+	have_event = client->packet_head != client->tail;
 	if (have_event) {
 		*event = client->buffer[client->tail++];
 		client->tail &= client->bufsize - 1;
-- 
1.7.3.1

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