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Commit640969a

Browse files
sthibaulgregkh
authored andcommitted
speakup: Fix clearing selection in safe context
speakup_cut() calls speakup_clear_selection() which calls console_lock.Problem is: speakup_cut() is called from a keyboard interruptcontext. This would hang if speakup_cut is pressed while the consolelock is unfortunately already held.We can however as well just defer calling clear_selection() until thealready-deferred set_selection_kernel() call.This was spotted by the lock hardener: Possible unsafe locking scenario:\x0a CPU0 ---- lock(console_lock); <Interrupt> lock(console_lock);\x0a *** DEADLOCK ***\x0a[...]Call Trace: <IRQ> dump_stack+0xc2/0x11a print_usage_bug.cold+0x3e0/0x4b1 mark_lock+0xd95/0x1390 ? print_irq_inversion_bug+0xa0/0xa0 __lock_acquire+0x21eb/0x5730 ? __kasan_check_read+0x11/0x20 ? check_chain_key+0x215/0x5e0 ? register_lock_class+0x1580/0x1580 ? lock_downgrade+0x7a0/0x7a0 ? __rwlock_init+0x140/0x140 lock_acquire+0x13f/0x370 ? speakup_clear_selection+0xe/0x20 [speakup] console_lock+0x33/0x50 ? speakup_clear_selection+0xe/0x20 [speakup] speakup_clear_selection+0xe/0x20 [speakup] speakup_cut+0x19e/0x4b0 [speakup] keyboard_notifier_call+0x1f04/0x4a40 [speakup] ? read_all_doc+0x240/0x240 [speakup] notifier_call_chain+0xbf/0x130 __atomic_notifier_call_chain+0x80/0x130 atomic_notifier_call_chain+0x16/0x20 kbd_event+0x7d7/0x3b20 ? k_pad+0x850/0x850 ? sysrq_filter+0x450/0xd40 input_to_handler+0x362/0x4b0 ? rcu_read_lock_sched_held+0xe0/0xe0 input_pass_values+0x408/0x5a0 ? __rwlock_init+0x140/0x140 ? lock_acquire+0x13f/0x370 input_handle_event+0x70e/0x1380 input_event+0x67/0x90 atkbd_interrupt+0xe62/0x1d4e [atkbd] ? __kasan_check_write+0x14/0x20 ? atkbd_event_work+0x130/0x130 [atkbd] ? _raw_spin_lock_irqsave+0x26/0x70 serio_interrupt+0x93/0x120 [serio] i8042_interrupt+0x232/0x510 [i8042] ? rcu_read_lock_bh_held+0xd0/0xd0 ? handle_irq_event+0xa5/0x13a ? i8042_remove+0x1f0/0x1f0 [i8042] __handle_irq_event_percpu+0xe6/0x6c0 handle_irq_event_percpu+0x71/0x150 ? __handle_irq_event_percpu+0x6c0/0x6c0 ? __kasan_check_read+0x11/0x20 ? do_raw_spin_unlock+0x5c/0x240 handle_irq_event+0xad/0x13a handle_edge_irq+0x233/0xa90 do_IRQ+0x10b/0x310 common_interrupt+0xf/0xf </IRQ>Cc: stable@vger.kernel.orgReported-by: Jookia <contact@jookia.org>Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>Link:https://lore.kernel.org/r/20201107233310.7iisvaozpiqj3yvy@functionSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 parentd7012df commit640969a

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3 files changed

+4
-9
lines changed

3 files changed

+4
-9
lines changed

‎drivers/accessibility/speakup/main.c‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -357,7 +357,6 @@ static void speakup_cut(struct vc_data *vc)
357357
mark_cut_flag=0;
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synth_printf("%s\n",spk_msg_get(MSG_CUT));
359359

360-
speakup_clear_selection();
361360
ret=speakup_set_selection(tty);
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363362
switch (ret) {

‎drivers/accessibility/speakup/selection.c‎

Lines changed: 4 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -22,13 +22,6 @@ struct speakup_selection_work {
2222
structtty_struct*tty;
2323
};
2424

25-
voidspeakup_clear_selection(void)
26-
{
27-
console_lock();
28-
clear_selection();
29-
console_unlock();
30-
}
31-
3225
staticvoid__speakup_set_selection(structwork_struct*work)
3326
{
3427
structspeakup_selection_work*ssw=
@@ -51,6 +44,10 @@ static void __speakup_set_selection(struct work_struct *work)
5144
gotounref;
5245
}
5346

47+
console_lock();
48+
clear_selection();
49+
console_unlock();
50+
5451
set_selection_kernel(&sel,tty);
5552

5653
unref:

‎drivers/accessibility/speakup/speakup.h‎

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -70,7 +70,6 @@ void spk_do_flush(void);
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voidspeakup_start_ttys(void);
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voidsynth_buffer_add(u16ch);
7272
voidsynth_buffer_clear(void);
73-
voidspeakup_clear_selection(void);
7473
intspeakup_set_selection(structtty_struct*tty);
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voidspeakup_cancel_selection(void);
7675
intspeakup_paste_selection(structtty_struct*tty);

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