blob: 4bfa1d253808f955bdf205e38a63b8be07d5caff [file] [log] [blame]
From af6ffe8c5fab9644ac285d3bc6e370866e31e419 Mon Sep 17 00:00:00 2001
From: Qiujun Huang <hqjagain@gmail.com>
Date: Sun, 29 Mar 2020 16:56:47 +0800
Subject: [PATCH] fbcon: fix null-ptr-deref in fbcon_switch
commit b139f8b00db4a8ea75a4174346eafa48041aa489 upstream.
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@syzkaller.appspotmail.com
Signed-off-by: Qiujun Huang <hqjagain@gmail.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200329085647.25133-1-hqjagain@gmail.com
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index a9c69ae30878..405ce0357f1b 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1254,6 +1254,9 @@ 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;
}
--
2.7.4