From: Samuel Thibault samuel.thibault@ens-lyon.org
commit 640969a69ca4dd2ac025fe873c6bf25eba8f11b3 upstream.
speakup_cut() calls speakup_clear_selection() which calls console_lock. Problem is: speakup_cut() is called from a keyboard interrupt context. This would hang if speakup_cut is pressed while the console lock is unfortunately already held.
We can however as well just defer calling clear_selection() until the already-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.org Reported-by: Jookia contact@jookia.org Signed-off-by: Samuel Thibault samuel.thibault@ens-lyon.org Link: https://lore.kernel.org/r/20201107233310.7iisvaozpiqj3yvy@function Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/accessibility/speakup/main.c | 1 - drivers/accessibility/speakup/selection.c | 11 ++++------- drivers/accessibility/speakup/speakup.h | 1 - 3 files changed, 4 insertions(+), 9 deletions(-)
--- a/drivers/accessibility/speakup/main.c +++ b/drivers/accessibility/speakup/main.c @@ -357,7 +357,6 @@ static void speakup_cut(struct vc_data * mark_cut_flag = 0; synth_printf("%s\n", spk_msg_get(MSG_CUT));
- speakup_clear_selection(); ret = speakup_set_selection(tty);
switch (ret) { --- a/drivers/accessibility/speakup/selection.c +++ b/drivers/accessibility/speakup/selection.c @@ -22,13 +22,6 @@ struct speakup_selection_work { struct tty_struct *tty; };
-void speakup_clear_selection(void) -{ - console_lock(); - clear_selection(); - console_unlock(); -} - static void __speakup_set_selection(struct work_struct *work) { struct speakup_selection_work *ssw = @@ -51,6 +44,10 @@ static void __speakup_set_selection(stru goto unref; }
+ console_lock(); + clear_selection(); + console_unlock(); + set_selection_kernel(&sel, tty);
unref: --- a/drivers/accessibility/speakup/speakup.h +++ b/drivers/accessibility/speakup/speakup.h @@ -70,7 +70,6 @@ void spk_do_flush(void); void speakup_start_ttys(void); void synth_buffer_add(u16 ch); void synth_buffer_clear(void); -void speakup_clear_selection(void); int speakup_set_selection(struct tty_struct *tty); void speakup_cancel_selection(void); int speakup_paste_selection(struct tty_struct *tty);