From: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> commit d4122754442799187d5d537a9c039a49a67e57f1 upstream. Speakup has only one speakup_tty variable to store the tty it is managing. This makes sense since its codebase currently assumes that there is only one user who controls the screen reading. That however means that we have to forbid using the line discipline several times, otherwise the second closure would try to free a NULL ldisc_data, leading to general protection fault: 0000 [#1] SMP KASAN PTI RIP: 0010:spk_ttyio_ldisc_close+0x2c/0x60 Call Trace: tty_ldisc_release+0xa2/0x340 tty_release_struct+0x17/0xd0 tty_release+0x9d9/0xcc0 __fput+0x231/0x740 task_work_run+0x12c/0x1a0 do_exit+0x9b5/0x2230 ? release_task+0x1240/0x1240 ? __do_page_fault+0x562/0xa30 do_group_exit+0xd5/0x2a0 __x64_sys_exit_group+0x35/0x40 do_syscall_64+0x89/0x2b0 ? page_fault+0x8/0x30 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Cc: stable@xxxxxxxxxxxxxxx Reported-by: 秦世松 <qinshisong1205@xxxxxxxxx> Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx> Tested-by: Shisong Qin <qinshisong1205@xxxxxxxxx> Link: https://lore.kernel.org/r/20201110183541.fzgnlwhjpgqzjeth@function Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/staging/speakup/spk_ttyio.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/drivers/staging/speakup/spk_ttyio.c +++ b/drivers/staging/speakup/spk_ttyio.c @@ -49,15 +49,25 @@ static int spk_ttyio_ldisc_open(struct t if (tty->ops->write == NULL) return -EOPNOTSUPP; + + mutex_lock(&speakup_tty_mutex); + if (speakup_tty) { + mutex_unlock(&speakup_tty_mutex); + return -EBUSY; + } speakup_tty = tty; ldisc_data = kmalloc(sizeof(struct spk_ldisc_data), GFP_KERNEL); - if (!ldisc_data) + if (!ldisc_data) { + speakup_tty = NULL; + mutex_unlock(&speakup_tty_mutex); return -ENOMEM; + } sema_init(&ldisc_data->sem, 0); ldisc_data->buf_free = true; speakup_tty->disc_data = ldisc_data; + mutex_unlock(&speakup_tty_mutex); return 0; }
