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Commit ff818b44 authored by Grzegorz Halat's avatar Grzegorz Halat Committed by Greg Kroah-Hartman
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vt/fbcon: deinitialize resources in visual_init() after failed memory allocation 



commit a1ad1cc9704f64c169261a76e1aee1cf1ae51832 upstream.

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: default avatarGrzegorz Halat <ghalat@redhat.com>
Reviewed-by: default avatarOleksandr Natalenko <oleksandr@redhat.com>
Acked-by: default avatarBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6e322a9e

drivers/tty/vt/vt.c

+9 −2
Original line number Diff line number Diff line
@@ -1059,6 +1059,13 @@ 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;
@@ -1106,6 +1113,7 @@ 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;
@@ -1334,9 +1342,8 @@ 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
@@ -1237,7 +1237,7 @@ 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))