queue-4.19/vt-fbcon-deinitialize-resources-in-visual_init-after-failed-memory-allocation.patch

   1 From a1ad1cc9704f64c169261a76e1aee1cf1ae51832 Mon Sep 17 00:00:00 2001
   2 From: Grzegorz Halat <ghalat@redhat.com>
   3 Date: Fri, 26 Apr 2019 16:59:46 +0200
   4 Subject: vt/fbcon: deinitialize resources in visual_init() after failed memory allocation
   5
   6 From: Grzegorz Halat <ghalat@redhat.com>
   7
   8 commit a1ad1cc9704f64c169261a76e1aee1cf1ae51832 upstream.
   9
  10 After memory allocation failure vc_allocate() doesn't clean up data
  11 which has been initialized in visual_init(). In case of fbcon this
  12 leads to divide-by-0 in fbcon_init() on next open of the same tty.
  13
  14 memory allocation in vc_allocate() may fail here:
  15 1097:     vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_KERNEL);
  16
  17 on next open() fbcon_init() skips vc_font.data initialization:
  18 1088:     if (!p->fontdata) {
  19
  20 division by zero in fbcon_init() happens here:
  21 1149:     new_cols /= vc->vc_font.width;
  22
  23 Additional check is needed in fbcon_deinit() to prevent
  24 usage of uninitialized vc_screenbuf:
  25
  26 1251:        if (vc->vc_hi_font_mask && vc->vc_screenbuf)
  27 1252:                set_vc_hi_font(vc, false);
  28
  29 Crash:
  30
  31  #6 [ffffc90001eafa60] divide_error at ffffffff81a00be4
  32     [exception RIP: fbcon_init+463]
  33     RIP: ffffffff814b860f  RSP: ffffc90001eafb18  RFLAGS: 00010246
  34 ...
  35  #7 [ffffc90001eafb60] visual_init at ffffffff8154c36e
  36  #8 [ffffc90001eafb80] vc_allocate at ffffffff8154f53c
  37  #9 [ffffc90001eafbc8] con_install at ffffffff8154f624
  38 ...
  39
  40 Signed-off-by: Grzegorz Halat <ghalat@redhat.com>
  41 Reviewed-by: Oleksandr Natalenko <oleksandr@redhat.com>
  42 Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
  43 Cc: stable <stable@vger.kernel.org>
  44 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  45
  46 ---
  47  drivers/tty/vt/vt.c              |   11 +++++++++--
  48  drivers/video/fbdev/core/fbcon.c |    2 +-
  49  2 files changed, 10 insertions(+), 3 deletions(-)
  50
  51 --- a/drivers/tty/vt/vt.c
  52 +++ b/drivers/tty/vt/vt.c
  53 @@ -1059,6 +1059,13 @@ static void visual_init(struct vc_data *
  54         vc->vc_screenbuf_size = vc->vc_rows * vc->vc_size_row;
  55  }
  56
  57 +
  58 +static void visual_deinit(struct vc_data *vc)
  59 +{
  60 +       vc->vc_sw->con_deinit(vc);
  61 +       module_put(vc->vc_sw->owner);
  62 +}
  63 +
  64  int vc_allocate(unsigned int currcons) /* return 0 on success */
  65  {
  66         struct vt_notifier_param param;
  67 @@ -1106,6 +1113,7 @@ int vc_allocate(unsigned int currcons)    /
  68
  69         return 0;
  70  err_free:
  71 +       visual_deinit(vc);
  72         kfree(vc);
  73         vc_cons[currcons].d = NULL;
  74         return -ENOMEM;
  75 @@ -1334,9 +1342,8 @@ struct vc_data *vc_deallocate(unsigned i
  76                 param.vc = vc = vc_cons[currcons].d;
  77                 atomic_notifier_call_chain(&vt_notifier_list, VT_DEALLOCATE, &param);
  78                 vcs_remove_sysfs(currcons);
  79 -               vc->vc_sw->con_deinit(vc);
  80 +               visual_deinit(vc);
  81                 put_pid(vc->vt_pid);
  82 -               module_put(vc->vc_sw->owner);
  83                 vc_uniscr_set(vc, NULL);
  84                 kfree(vc->vc_screenbuf);
  85                 vc_cons[currcons].d = NULL;
  86 --- a/drivers/video/fbdev/core/fbcon.c
  87 +++ b/drivers/video/fbdev/core/fbcon.c
  88 @@ -1237,7 +1237,7 @@ finished:
  89         if (free_font)
  90                 vc->vc_font.data = NULL;
  91
  92 -       if (vc->vc_hi_font_mask)
  93 +       if (vc->vc_hi_font_mask && vc->vc_screenbuf)
  94                 set_vc_hi_font(vc, false);
  95
  96         if (!con_is_bound(&fb_con))