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Input: evdev - only allow reading events if a full packet is present

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Without this, it was possible for the reader to get ahead of packet_head.
If 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.

Signed-off-by: Dima Zavin <dima@android.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
This commit is contained in:
Dima Zavin 2011-12-30 15:16:44 -08:00 committed by Dmitry Torokhov
parent 36a281e252
commit 566cf5b6e3
1 changed files with 1 additions and 1 deletions
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2
drivers/input/evdev.c
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@ -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;