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authorQiujun Huang <hqjagain@gmail.com>2020-03-29 16:56:47 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-04-13 13:18:12 +0200
commit5c46deb2cb626b201536245ed9372f7de666b6b8 (patch)
treea33d1aa5d81fdc2bd47fe6a849d900d9eca0ecfc
parentd3e7c575aa035d8f95f80bf2b13126a235b0167b (diff)
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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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/video/fbdev/core/fbcon.c3
1 files changed, 3 insertions, 0 deletions
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 @@ finished:
if (!con_is_bound(&fb_con))
fbcon_exit();
+ if (vc->vc_num == logo_shown)
+ logo_shown = FBCON_LOGO_CANSHOW;
+
return;
}