From: George Kennedy george.kennedy@oracle.com
commit 39b3cffb8cf3111738ea993e2757ab382253d86a upstream.
Add a check to fbcon_resize() to ensure that a possible change to user font height or user font width will not allow a font data out-of-bounds access. NOTE: must use original charcount in calculation as font charcount can change and cannot be used to determine the font data allocated size.
Signed-off-by: George Kennedy george.kennedy@oracle.com Cc: stable stable@vger.kernel.org Reported-by: syzbot+38a3699c7eaf165b97a6@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/1596213192-6635-1-git-send-email-george.kennedy@or... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/video/fbdev/core/fbcon.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-)
--- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2130,6 +2130,9 @@ static void updatescrollmode(struct disp } }
+#define PITCH(w) (((w) + 7) >> 3) +#define CALC_FONTSZ(h, p, c) ((h) * (p) * (c)) /* size = height * pitch * charcount */ + static int fbcon_resize(struct vc_data *vc, unsigned int width, unsigned int height, unsigned int user) { @@ -2139,6 +2142,24 @@ static int fbcon_resize(struct vc_data * struct fb_var_screeninfo var = info->var; int x_diff, y_diff, virt_w, virt_h, virt_fw, virt_fh;
+ if (ops->p && ops->p->userfont && FNTSIZE(vc->vc_font.data)) { + int size; + int pitch = PITCH(vc->vc_font.width); + + /* + * If user font, ensure that a possible change to user font + * height or width will not allow a font data out-of-bounds access. + * NOTE: must use original charcount in calculation as font + * charcount can change and cannot be used to determine the + * font data allocated size. + */ + if (pitch <= 0) + return -EINVAL; + size = CALC_FONTSZ(vc->vc_font.height, pitch, FNTCHARCNT(vc->vc_font.data)); + if (size > FNTSIZE(vc->vc_font.data)) + return -EINVAL; + } + virt_w = FBCON_SWAP(ops->rotate, width, height); virt_h = FBCON_SWAP(ops->rotate, height, width); virt_fw = FBCON_SWAP(ops->rotate, vc->vc_font.width, @@ -2600,7 +2621,7 @@ static int fbcon_set_font(struct vc_data int size; int i, csum; u8 *new_data, *data = font->data; - int pitch = (font->width+7) >> 3; + int pitch = PITCH(font->width);
/* Is there a reason why fbconsole couldn't handle any charcount >256? * If not this check should be changed to charcount < 256 */ @@ -2616,7 +2637,7 @@ static int fbcon_set_font(struct vc_data if (fbcon_invalid_charcount(info, charcount)) return -EINVAL;
- size = h * pitch * charcount; + size = CALC_FONTSZ(h, pitch, charcount);
new_data = kmalloc(FONT_EXTRA_WORDS * sizeof(int) + size, GFP_USER);