queue-4.19/tty-serial_core-add-install.patch

   1 From 4cdd17ba1dff20ffc99fdbd2e6f0201fc7fe67df Mon Sep 17 00:00:00 2001
   2 From: Jiri Slaby <jslaby@suse.cz>
   3 Date: Wed, 17 Apr 2019 10:58:53 +0200
   4 Subject: TTY: serial_core, add ->install
   5
   6 From: Jiri Slaby <jslaby@suse.cz>
   7
   8 commit 4cdd17ba1dff20ffc99fdbd2e6f0201fc7fe67df upstream.
   9
  10 We need to compute the uart state only on the first open. This is
  11 usually what is done in the ->install hook. serial_core used to do this
  12 in ->open on every open. So move it to ->install.
  13
  14 As a side effect, it ensures the state is set properly in the window
  15 after tty_init_dev is called, but before uart_open. This fixes a bunch
  16 of races between tty_open and flush_to_ldisc we were dealing with
  17 recently.
  18
  19 One of such bugs was attempted to fix in commit fedb5760648a (serial:
  20 fix race between flush_to_ldisc and tty_open), but it only took care of
  21 a couple of functions (uart_start and uart_unthrottle).  I was able to
  22 reproduce the crash on a SLE system, but in uart_write_room which is
  23 also called from flush_to_ldisc via process_echoes. I was *unable* to
  24 reproduce the bug locally. It is due to having this patch in my queue
  25 since 2012!
  26
  27  general protection fault: 0000 [#1] SMP KASAN PTI
  28  CPU: 1 PID: 5 Comm: kworker/u4:0 Tainted: G             L 4.12.14-396-default #1 SLE15-SP1 (unreleased)
  29  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c89-prebuilt.qemu.org 04/01/2014
  30  Workqueue: events_unbound flush_to_ldisc
  31  task: ffff8800427d8040 task.stack: ffff8800427f0000
  32  RIP: 0010:uart_write_room+0xc4/0x590
  33  RSP: 0018:ffff8800427f7088 EFLAGS: 00010202
  34  RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
  35  RDX: 000000000000002f RSI: 00000000000000ee RDI: ffff88003888bd90
  36  RBP: ffffffffb9545850 R08: 0000000000000001 R09: 0000000000000400
  37  R10: ffff8800427d825c R11: 000000000000006e R12: 1ffff100084fee12
  38  R13: ffffc900004c5000 R14: ffff88003888bb28 R15: 0000000000000178
  39  FS:  0000000000000000(0000) GS:ffff880043300000(0000) knlGS:0000000000000000
  40  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  41  CR2: 0000561da0794148 CR3: 000000000ebf4000 CR4: 00000000000006e0
  42  Call Trace:
  43   tty_write_room+0x6d/0xc0
  44   __process_echoes+0x55/0x870
  45   n_tty_receive_buf_common+0x105e/0x26d0
  46   tty_ldisc_receive_buf+0xb7/0x1c0
  47   tty_port_default_receive_buf+0x107/0x180
  48   flush_to_ldisc+0x35d/0x5c0
  49 ...
  50
  51 0 in rbx means tty->driver_data is NULL in uart_write_room. 0x178 is
  52 tried to be dereferenced (0x178 >> 3 is 0x2f in rdx) at
  53 uart_write_room+0xc4. 0x178 is exactly (struct uart_state *)NULL->refcount
  54 used in uart_port_lock from uart_write_room.
  55
  56 So revert the upstream commit here as my local patch should fix the
  57 whole family.
  58
  59 Signed-off-by: Jiri Slaby <jslaby@suse.cz>
  60 Cc: Li RongQing <lirongqing@baidu.com>
  61 Cc: Wang Li <wangli39@baidu.com>
  62 Cc: Zhang Yu <zhangyu31@baidu.com>
  63 Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  64 Cc: stable <stable@vger.kernel.org>
  65 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  66
  67 ---
  68  drivers/tty/serial/serial_core.c |   24 +++++++++++++-----------
  69  1 file changed, 13 insertions(+), 11 deletions(-)
  70
  71 --- a/drivers/tty/serial/serial_core.c
  72 +++ b/drivers/tty/serial/serial_core.c
  73 @@ -130,9 +130,6 @@ static void uart_start(struct tty_struct
  74         struct uart_port *port;
  75         unsigned long flags;
  76
  77 -       if (!state)
  78 -               return;
  79 -
  80         port = uart_port_lock(state, flags);
  81         __uart_start(tty);
  82         uart_port_unlock(port, flags);
  83 @@ -730,9 +727,6 @@ static void uart_unthrottle(struct tty_s
  84         upstat_t mask = UPSTAT_SYNC_FIFO;
  85         struct uart_port *port;
  86
  87 -       if (!state)
  88 -               return;
  89 -
  90         port = uart_port_ref(state);
  91         if (!port)
  92                 return;
  93 @@ -1708,6 +1702,16 @@ static void uart_dtr_rts(struct tty_port
  94         uart_port_deref(uport);
  95  }
  96
  97 +static int uart_install(struct tty_driver *driver, struct tty_struct *tty)
  98 +{
  99 +       struct uart_driver *drv = driver->driver_state;
 100 +       struct uart_state *state = drv->state + tty->index;
 101 +
 102 +       tty->driver_data = state;
 103 +
 104 +       return tty_standard_install(driver, tty);
 105 +}
 106 +
 107  /*
 108   * Calls to uart_open are serialised by the tty_lock in
 109   *   drivers/tty/tty_io.c:tty_open()
 110 @@ -1720,11 +1724,8 @@ static void uart_dtr_rts(struct tty_port
 111   */
 112  static int uart_open(struct tty_struct *tty, struct file *filp)
 113  {
 114 -       struct uart_driver *drv = tty->driver->driver_state;
 115 -       int retval, line = tty->index;
 116 -       struct uart_state *state = drv->state + line;
 117 -
 118 -       tty->driver_data = state;
 119 +       struct uart_state *state = tty->driver_data;
 120 +       int retval;
 121
 122         retval = tty_port_open(&state->port, tty, filp);
 123         if (retval > 0)
 124 @@ -2409,6 +2410,7 @@ static void uart_poll_put_char(struct tt
 125  #endif
 126
 127  static const struct tty_operations uart_ops = {
 128 +       .install        = uart_install,
 129         .open           = uart_open,
 130         .close          = uart_close,
 131         .write          = uart_write,