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Commit 96fe2ab8 authored by Johannes Weiner's avatar Johannes Weiner Committed by Jiri Kosina
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HID: fix waitqueue usage in hiddev 



DECLARE_WAITQUEUE doesn't initialize the wait descriptor's task_list
to 'empty' but to zero.

prepare_to_wait() will not enqueue the descriptor to the waitqueue and
finish_wait() will do list_del_init() on a list head that contains
NULL pointers, which oopses.

This was introduced by 07903407 "HID: hiddev cleanup -- handle all
error conditions properly".

The prior code used an unconditional add_to_waitqueue() which didn't
care about the wait descriptor's list head and enqueued the thing
unconditionally.

The new code uses prepare_to_wait() which DOES check the prior list
state, so use DEFINE_WAIT instead.

Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Cc: Oliver Neukum <oliver@neukum.name>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 48e7a3c9

drivers/hid/usbhid/hiddev.c

+1 −1
Original line number Diff line number Diff line
@@ -323,7 +323,7 @@ static ssize_t hiddev_write(struct file * file, const char __user * buffer, size 
 */

static ssize_t hiddev_read(struct file * file, char __user * buffer, size_t count, loff_t *ppos)

{

	DECLARE_WAITQUEUE(wait, current);

	DEFINE_WAIT(wait);

	struct hiddev_list *list = file->private_data;

	int event_size;

	int retval;