Hi Qiujun On Sun, Mar 29, 2020 at 04:56:47PM +0800, Qiujun Huang wrote: > Set logo_shown to FBCON_LOGO_CANSHOW when the vc was deallocated. > > syzkaller report: https://lkml.org/lkml/2020/3/27/403 > general protection fault, probably for non-canonical address > 0xdffffc000000006c: 0000 [#1] SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000360-0x0000000000000367] > RIP: 0010:fbcon_switch+0x28f/0x1740 > drivers/video/fbdev/core/fbcon.c:2260 > > Call Trace: > redraw_screen+0x2a8/0x770 drivers/tty/vt/vt.c:1008 > vc_do_resize+0xfe7/0x1360 drivers/tty/vt/vt.c:1295 > fbcon_init+0x1221/0x1ab0 drivers/video/fbdev/core/fbcon.c:1219 > visual_init+0x305/0x5c0 drivers/tty/vt/vt.c:1062 > do_bind_con_driver+0x536/0x890 drivers/tty/vt/vt.c:3542 > do_take_over_console+0x453/0x5b0 drivers/tty/vt/vt.c:4122 > do_fbcon_takeover+0x10b/0x210 drivers/video/fbdev/core/fbcon.c:588 > fbcon_fb_registered+0x26b/0x340 drivers/video/fbdev/core/fbcon.c:3259 > do_register_framebuffer drivers/video/fbdev/core/fbmem.c:1664 [inline] > register_framebuffer+0x56e/0x980 drivers/video/fbdev/core/fbmem.c:1832 > dlfb_usb_probe.cold+0x1743/0x1ba3 drivers/video/fbdev/udlfb.c:1735 > usb_probe_interface+0x310/0x800 drivers/usb/core/driver.c:374 > > accessing vc_cons[logo_shown].d->vc_top causes the bug. > > Reported-by: syzbot+732528bae351682f1f27@xxxxxxxxxxxxxxxxxxxxxxxxx > Signed-off-by: Qiujun Huang <hqjagain@xxxxxxxxx> > --- > drivers/video/fbdev/core/fbcon.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c > index bb6ae995c2e5..5eb3fc90f9f6 100644 > --- a/drivers/video/fbdev/core/fbcon.c > +++ b/drivers/video/fbdev/core/fbcon.c > @@ -1283,6 +1283,9 @@ static void fbcon_deinit(struct vc_data *vc) > if (!con_is_bound(&fb_con)) > fbcon_exit(); > > + if (vc->vc_num == logo_shown) > + logo_shown = FBCON_LOGO_CANSHOW; > + > return; > } Looks much better than the previous version. Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx> I expect Bartlomiej to review/apply. Sam _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
