From: Sam Ravnborg <sam@ravnborg.org>
To: Yang Yingliang <yangyingliang@huawei.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: b.zolnierkie@samsung.com, linux-fbdev@vger.kernel.org,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] vgacon: fix a UAF in do_update_region()
Date: Sat, 17 Oct 2020 14:25:06 +0200 [thread overview]
Message-ID: <20201017122506.GA2838103@ravnborg.org> (raw)
In-Reply-To: <20200713110445.553974-1-yangyingliang@huawei.com>
Hi Yang.
Can you please resend and include Greg in the recipient list.
Greg is maintainer of the console subsystem these days.
Sam
On Mon, Jul 13, 2020 at 11:04:45AM +0000, Yang Yingliang wrote:
> I got a UAF report in do_update_region() when I doing fuzz test.
>
> [ 51.161905] BUG: KASAN: use-after-free in do_update_region+0x579/0x600
> [ 51.161918] Read of size 2 at addr ffff888000100000 by task test/295
>
> [ 51.161957] CPU: 2 PID: 295 Comm: test Not tainted 5.7.0+ #975
> [ 51.161969] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> [ 51.161976] Call Trace:
> [ 51.162001] dump_stack+0xc6/0x11e
> [ 51.162019] ? do_update_region+0x579/0x600
> [ 51.162047] print_address_description.constprop.6+0x1a/0x220
> [ 51.162083] ? vprintk_func+0x66/0xed
> [ 51.162100] ? do_update_region+0x579/0x600
> [ 51.162112] ? do_update_region+0x579/0x600
> [ 51.162128] kasan_report.cold.9+0x37/0x7c
> [ 51.162151] ? do_update_region+0x579/0x600
> [ 51.162173] do_update_region+0x579/0x600
> [ 51.162207] ? con_get_trans_old+0x230/0x230
> [ 51.162229] ? retint_kernel+0x10/0x10
> [ 51.162278] csi_J+0x557/0xa00
> [ 51.162307] do_con_trol+0x49af/0x5cc0
> [ 51.162330] ? lock_downgrade+0x720/0x720
> [ 51.162347] ? reset_palette+0x1b0/0x1b0
> [ 51.162369] ? lockdep_hardirqs_on_prepare+0x379/0x540
> [ 51.162393] ? notifier_call_chain+0x11b/0x160
> [ 51.162438] do_con_write.part.24+0xb0a/0x1a30
> [ 51.162501] ? do_con_trol+0x5cc0/0x5cc0
> [ 51.162522] ? console_unlock+0x7b8/0xb00
> [ 51.162555] ? __mutex_unlock_slowpath+0xd4/0x670
> [ 51.162574] ? this_tty+0xe0/0xe0
> [ 51.162589] ? console_unlock+0x559/0xb00
> [ 51.162605] ? wait_for_completion+0x260/0x260
> [ 51.162638] con_write+0x31/0xb0
> [ 51.162658] n_tty_write+0x4fa/0xd40
> [ 51.162710] ? n_tty_read+0x1800/0x1800
> [ 51.162730] ? prepare_to_wait_exclusive+0x270/0x270
> [ 51.162754] ? __might_fault+0x175/0x1b0
> [ 51.162783] tty_write+0x42b/0x8d0
> [ 51.162795] ? n_tty_read+0x1800/0x1800
> [ 51.162825] ? tty_lookup_driver+0x450/0x450
> [ 51.162848] __vfs_write+0x7c/0x100
> [ 51.162875] vfs_write+0x1c9/0x510
> [ 51.162901] ksys_write+0xff/0x200
> [ 51.162918] ? __ia32_sys_read+0xb0/0xb0
> [ 51.162940] ? do_syscall_64+0x1a/0x520
> [ 51.162957] ? lockdep_hardirqs_on_prepare+0x379/0x540
> [ 51.162984] do_syscall_64+0xa1/0x520
> [ 51.163008] entry_SYSCALL_64_after_hwframe+0x49/0xb3
>
> After vgacon_set_origin() is called in set_origin(), the vc_origin is
> set to vga_vram_base, the vc_pos should between vga_vram_base and
> vga_vram_end. But we still use vc_screenbuf_size, if the vga_vram_size
> is smaller than vc_screenbuf_size, vc_pos may be out of bound, using it
> will cause a use-after-free(or out-of-bounds). Fix this by calling
> vc_resize() if vga_vram_size is smaller than vc_screenbuf_size.
>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
> drivers/video/console/vgacon.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
> index b51ffb9a208d..2eabb86bb0dd 100644
> --- a/drivers/video/console/vgacon.c
> +++ b/drivers/video/console/vgacon.c
> @@ -1341,6 +1341,9 @@ static int vgacon_set_origin(struct vc_data *c)
> if (vga_is_gfx || /* We don't play origin tricks in graphic modes */
> (console_blanked && !vga_palette_blanked)) /* Nor we write to blanked screens */
> return 0;
> +
> + if (c->vc_screenbuf_size > vga_vram_size)
> + vc_resize(c, screen_info.orig_video_cols, screen_info.orig_video_lines);
> c->vc_origin = c->vc_visible_origin = vga_vram_base;
> vga_set_mem_top(c);
> vga_rolled_over = 0;
> --
> 2.25.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2020-10-17 12:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 11:04 [PATCH] vgacon: fix a UAF in do_update_region() Yang Yingliang
2020-10-17 12:25 ` Sam Ravnborg [this message]
2020-10-20 9:02 ` [PATCH resend] " Yang Yingliang
2020-10-20 9:20 ` Yang Yingliang
[not found] <CGME20200604141553eucas1p185479b18995247931b3e79288f2496a9@eucas1p1.samsung.com>
2020-06-04 14:38 ` [PATCH] " Yang Yingliang
2020-07-10 10:47 ` Bartlomiej Zolnierkiewicz
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