On 4/26/19 4:59 PM, Grzegorz Halat wrote:
> 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@xxxxxxxxxx>
Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics
