[patch 1/1] [patch] staging: speakup: fix speakup-r empty line lockup

Okash Khawaja
2017-09-05T10:51:39Z

[-- Attachment #1: speakup-r-fix.patch --]
[-- Type: text/plain, Size: 2550 bytes --]

When cursor is at beginning of an empty or whitespace-only line and
speakup-r typed, kernel locks up. This happens because deadlock of in
input_event function over dev->event_lock, as demonstrated by lockdep
logs. The reason for that is speakup simulates a down arrow - because
cursor is at an empty line - while inside key press notifier handler
which is ultimately triggered from input_event function. The simulated
key press leads to input_event being called again, this time under its
own context. So the spinlock is dev->event_lock is acquired while still
being held.

This patch ensures that key press is not simulated from inside key press
notifier handler. Instead it delegates to cursor_timer. It starts the
timer and passes RA_DOWN_ARROW as argument. When timer handler runs and
sees RA_DOWN_ARROW, it will then call kbd_fakekey2(RA_DOWN_ARROW) which
will correctly simulate the keypress inside timer context.

When not inside key press notifier callback, the behaviour will remain
the same as before this patch.

Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

---
drivers/staging/speakup/main.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

--- a/drivers/staging/speakup/main.c
+++ b/drivers/staging/speakup/main.c
@@ -1376,6 +1376,8 @@ static void reset_highlight_buffers(stru

static int read_all_key;

+static int in_keyboard_notifier;
+
static void start_read_all_timer(struct vc_data *vc, int command);

enum {
@@ -1408,7 +1410,10 @@ static void read_all_doc(struct vc_data
cursor_track = read_all_mode;
spk_reset_index_count(0);
if (get_sentence_buf(vc, 0) == -1) {
- kbd_fakekey2(vc, RA_DOWN_ARROW);
+ del_timer(&cursor_timer);
+ if (!in_keyboard_notifier)
+ speakup_fake_down_arrow();
+ start_read_all_timer(vc, RA_DOWN_ARROW);
} else {
say_sentence_num(0, 0);
synth_insert_next_index(0);
@@ -2212,8 +2217,10 @@ static int keyboard_notifier_call(struct
int ret = NOTIFY_OK;
static int keycode; /* to hold the current keycode */

+ in_keyboard_notifier = 1;
+
if (vc->vc_mode == KD_GRAPHICS)
- return ret;
+ goto out;

/*
* First, determine whether we are handling a fake keypress on
@@ -2225,7 +2232,7 @@ static int keyboard_notifier_call(struct
*/

if (speakup_fake_key_pressed())
- return ret;
+ goto out;

switch (code) {
case KBD_KEYCODE:
@@ -2266,6 +2273,8 @@ static int keyboard_notifier_call(struct
break;
}
}
+out:
+ in_keyboard_notifier = 0;
return ret;
}