Commit a5a92303 authored by Shigeru Yoshida's avatar Shigeru Yoshida Committed by Helge Deller
Browse files

fbdev: fbcon: Properly revert changes when vc_resize() failed 

fbcon_do_set_font() calls vc_resize() when font size is changed.
However, if if vc_resize() failed, current implementation doesn't
revert changes for font size, and this causes inconsistent state.

syzbot reported unable to handle page fault due to this issue [1].
syzbot's repro uses fault injection which cause failure for memory
allocation, so vc_resize() failed.

This patch fixes this issue by properly revert changes for font
related date when vc_resize() failed.

Link: https://syzkaller.appspot.com/bug?id=3443d3a1fa6d964dd7310a0cb1696d165a3e07c4

 [1]
Reported-by: default avatar <syzbot+a168dbeaaa7778273c1b@syzkaller.appspotmail.com>
Signed-off-by: default avatarShigeru Yoshida <syoshida@redhat.com>
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
CC: stable@vger.kernel.org # 5.15+
parent 8d026858

drivers/video/fbdev/core/fbcon.c

+25 −2
Original line number Diff line number Diff line
@@ -2401,15 +2401,21 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, 
	struct fb_info *info = fbcon_info_from_console(vc->vc_num);

	struct fbcon_ops *ops = info->fbcon_par;

	struct fbcon_display *p = &fb_display[vc->vc_num];

	int resize;

	int resize, ret, old_userfont, old_width, old_height, old_charcount;

	char *old_data = NULL;



	resize = (w != vc->vc_font.width) || (h != vc->vc_font.height);

	if (p->userfont)

		old_data = vc->vc_font.data;

	vc->vc_font.data = (void *)(p->fontdata = data);

	old_userfont = p->userfont;

	if ((p->userfont = userfont))

		REFCOUNT(data)++;



	old_width = vc->vc_font.width;

	old_height = vc->vc_font.height;

	old_charcount = vc->vc_font.charcount;



	vc->vc_font.width = w;

	vc->vc_font.height = h;

	vc->vc_font.charcount = charcount;
@@ -2425,7 +2431,9 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, 
		rows = FBCON_SWAP(ops->rotate, info->var.yres, info->var.xres);

		cols /= w;

		rows /= h;

		vc_resize(vc, cols, rows);

		ret = vc_resize(vc, cols, rows);

		if (ret)

			goto err_out;

	} else if (con_is_visible(vc)

		   && vc->vc_mode == KD_TEXT) {

		fbcon_clear_margins(vc, 0);
@@ -2435,6 +2443,21 @@ static int fbcon_do_set_font(struct vc_data *vc, int w, int h, int charcount, 
	if (old_data && (--REFCOUNT(old_data) == 0))

		kfree(old_data - FONT_EXTRA_WORDS * sizeof(int));

	return 0;



err_out:

	p->fontdata = old_data;

	vc->vc_font.data = (void *)old_data;



	if (userfont) {

		p->userfont = old_userfont;

		REFCOUNT(data)--;

	}



	vc->vc_font.width = old_width;

	vc->vc_font.height = old_height;

	vc->vc_font.charcount = old_charcount;



	return ret;

}



/*