This is a note to let you know that I've just added the patch titled

vt/fbcon: deinitialize resources in visual_init() after failed memory

to my tty git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From a1ad1cc9704f64c169261a76e1aee1cf1ae51832 Mon Sep 17 00:00:00 2001

From: Grzegorz Halat ghalat@redhat.com Date: Fri, 26 Apr 2019 16:59:46 +0200 Subject: vt/fbcon: deinitialize resources in visual_init() after failed memory allocation

After memory allocation failure vc_allocate() doesn't clean up data which has been initialized in visual_init(). In case of fbcon this leads to divide-by-0 in fbcon_init() on next open of the same tty.

memory allocation in vc_allocate() may fail here: 1097: vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_KERNEL);

on next open() fbcon_init() skips vc_font.data initialization: 1088: if (!p->fontdata) {

division by zero in fbcon_init() happens here: 1149: new_cols /= vc->vc_font.width;

Additional check is needed in fbcon_deinit() to prevent usage of uninitialized vc_screenbuf:

1251: if (vc->vc_hi_font_mask && vc->vc_screenbuf) 1252: set_vc_hi_font(vc, false);

Crash:

#6 [ffffc90001eafa60] divide_error at ffffffff81a00be4 [exception RIP: fbcon_init+463] RIP: ffffffff814b860f RSP: ffffc90001eafb18 RFLAGS: 00010246 ... #7 [ffffc90001eafb60] visual_init at ffffffff8154c36e #8 [ffffc90001eafb80] vc_allocate at ffffffff8154f53c #9 [ffffc90001eafbc8] con_install at ffffffff8154f624 ...

Signed-off-by: Grzegorz Halat ghalat@redhat.com Reviewed-by: Oleksandr Natalenko oleksandr@redhat.com Acked-by: Bartlomiej Zolnierkiewicz b.zolnierkie@samsung.com Cc: stable stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/vt/vt.c | 11 +++++++++-- drivers/video/fbdev/core/fbcon.c | 2 +- 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index fdd12f8c3deb..5c0ca1c24b6f 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -1056,6 +1056,13 @@ static void visual_init(struct vc_data *vc, int num, int init) vc->vc_screenbuf_size = vc->vc_rows * vc->vc_size_row; }

+ +static void visual_deinit(struct vc_data *vc) +{ + vc->vc_sw->con_deinit(vc); + module_put(vc->vc_sw->owner); +} + int vc_allocate(unsigned int currcons) /* return 0 on success */ { struct vt_notifier_param param; @@ -1103,6 +1110,7 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */

return 0; err_free: + visual_deinit(vc); kfree(vc); vc_cons[currcons].d = NULL; return -ENOMEM; @@ -1331,9 +1339,8 @@ struct vc_data *vc_deallocate(unsigned int currcons) param.vc = vc = vc_cons[currcons].d; atomic_notifier_call_chain(&vt_notifier_list, VT_DEALLOCATE, &param); vcs_remove_sysfs(currcons); - vc->vc_sw->con_deinit(vc); + visual_deinit(vc); put_pid(vc->vt_pid); - module_put(vc->vc_sw->owner); vc_uniscr_set(vc, NULL); kfree(vc->vc_screenbuf); vc_cons[currcons].d = NULL; diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 786f9aab55df..a9c69ae30878 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -1248,7 +1248,7 @@ static void fbcon_deinit(struct vc_data *vc) if (free_font) vc->vc_font.data = NULL;

- if (vc->vc_hi_font_mask) + if (vc->vc_hi_font_mask && vc->vc_screenbuf) set_vc_hi_font(vc, false);

if (!con_is_bound(&fb_con))