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; } -- 2.17.1 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
