Re: tty, fbcon: use-after-free in fbcon_invert_region
From: Scot Doyle <hidden>
Date: 2016-10-11 01:50:11
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On Fri, 7 Oct 2016, Dmitry Vyukov wrote:
On Sat, Sep 3, 2016 at 9:20 PM, Dmitry Vyukov [off-list ref] wrote:quoted
Hello, The following program causes use-after-free in fbcon_invert_region: https://gist.githubusercontent.com/dvyukov/d657f9a9ca39f34c430dcf63ec1153ac/raw/04e1b94aef0fc9eb770d11373b568980ecaa7f34/gistfile1.txt ================================= BUG: KASAN: use-after-free in fbcon_invert_region+0x1cc/0x1f0 at addr ffff88006cc3f51e Read of size 2 by task a.out/4240 CPU: 0 PID: 4240 Comm: a.out Not tainted 4.8.0-rc3-next-20160825+ #10 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 ffffffff886b6fe0 ffff88003699f790 ffffffff82db3759 ffffffff8a0ae640 fffffbfff10d6dfc ffff88003e800100 ffff88006cc3f500 ffff88006cc3f520 0000000000000000 ffff88006cc3f51e ffff88003699f7b8 ffffffff81809e7c Call Trace: [<ffffffff8180a474>] __asan_report_load2_noabort+0x14/0x20 mm/kasan/report.c:325 [<ffffffff82fdbc8c>] fbcon_invert_region+0x1cc/0x1f0 drivers/video/console/fbcon.c:2750 [<ffffffff8327ce72>] invert_screen+0x192/0x630 drivers/tty/vt/vt.c:470 [< inline >] highlight drivers/tty/vt/selection.c:50 [<ffffffff8326037c>] clear_selection+0x4c/0x60 drivers/tty/vt/selection.c:76 [<ffffffff8327374e>] hide_cursor+0x24e/0x2d0 drivers/tty/vt/vt.c:599 [<ffffffff83276207>] redraw_screen+0x2e7/0x840 drivers/tty/vt/vt.c:682 [<ffffffff83278b0c>] vc_do_resize+0xebc/0x1160 drivers/tty/vt/vt.c:952 [<ffffffff83278eba>] vt_resize+0xaa/0xe0 drivers/tty/vt/vt.c:992 [< inline >] tiocswinsz drivers/tty/tty_io.c:2378 [<ffffffff83224e71>] tty_ioctl+0x10c1/0x21e0 drivers/tty/tty_io.c:2892 [< inline >] vfs_ioctl fs/ioctl.c:43 [<ffffffff818a1c6c>] do_vfs_ioctl+0x18c/0x1080 fs/ioctl.c:675 [< inline >] SYSC_ioctl fs/ioctl.c:690 [<ffffffff818a2bef>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:681 [<ffffffff86e10480>] entry_SYSCALL_64_fastpath+0x23/0xc1
I wonder if the text selection is outside the newly resized vc? Does this patch help?
--- vt.c 2016-10-11 00:32:43.079605599 -0000
+++ vt.c.new 2016-10-11 00:36:12.744650759 -0000@@ -874,6 +874,9 @@ if (!newscreen) return -ENOMEM; + if (vc = sel_cons) + clear_selection(); + old_rows = vc->vc_rows; old_row_size = vc->vc_size_row;