Commit 5e309c6c authored Apr 26, 2019 by Grzegorz Halat Committed by Greg Kroah-Hartman May 24, 2019

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 84ecc2f6

drivers/tty/vt/vt.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -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;

drivers/video/fbdev/core/fbcon.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1248,7 +1248,7 @@ finished:
		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))

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