From: Jiri Slaby <jirislaby@kernel.org>
To: 张云海 <zhangyunhai@nsfocus.com>, b.zolnierkie@samsung.com
Cc: linux-kernel@vger.kernel.org,
Yang Yingliang <yangyingliang@huawei.com>,
Kyungtae Kim <kt0755@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Greg KH <greg@kroah.com>, Solar Designer <solar@openwall.com>,
"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>,
Anthony Liguori <aliguori@amazon.com>,
Security Officers <security@kernel.org>,
linux-distros@vs.openwall.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org
Subject: Re: [PATCH] vgacon: fix out of bounds write to the scrollback buffer
Date: Wed, 29 Jul 2020 10:11:57 +0200 [thread overview]
Message-ID: <c1f267aa-dfb3-91fa-3111-30c1676f1a91@kernel.org> (raw)
In-Reply-To: <55075898-bf95-1805-3358-b0d1438feaa9@nsfocus.com>
Hi,
On 29. 07. 20, 9:53, 张云海 wrote:
> This patch dosen't fix the issue, the check should be in the loop.
>
> The change of the VT sze is before vgacon_scrollback_update, not in the
> meantime.
>
> Let's consider the following situation:
> suppose:
> vgacon_scrollback_cur->size is 65440
> vgacon_scrollback_cur->tail is 64960
> c->vc_size_row is 160
> count is 5
>
> Reset c->vc_size_row to 200 by VT_RESIZE, then call
> vgacon_scrollback_update.
>
> This will pass the check, since (vgacon_scrollback_cur->tail +
> c->vc_size_row)
> is 65160 which is less then vgacon_scrollback_cur->size(65440).
>
> However, in the 3rd iteration of the loop, vgacon_scrollback_cur->tail
> is update
> to 65360, the memcpy will overflow.
But the loop checks for the overflow:
if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
vgacon_scrollback_cur->tail = 0;
So the first 2 iterations would write to the end of the buffer and this
3rd one should have zeroed ->tail.
thanks,
--
js
suse labs
WARNING: multiple messages have this Message-ID (diff)
From: Jiri Slaby <jirislaby@kernel.org>
To: 张云海 <zhangyunhai@nsfocus.com>, b.zolnierkie@samsung.com
Cc: Security Officers <security@kernel.org>,
Kyungtae Kim <kt0755@gmail.com>,
Anthony Liguori <aliguori@amazon.com>, Greg KH <greg@kroah.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-distros@vs.openwall.org,
Solar Designer <solar@openwall.com>,
Yang Yingliang <yangyingliang@huawei.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>
Subject: Re: [PATCH] vgacon: fix out of bounds write to the scrollback buffer
Date: Wed, 29 Jul 2020 08:11:57 +0000 [thread overview]
Message-ID: <c1f267aa-dfb3-91fa-3111-30c1676f1a91@kernel.org> (raw)
In-Reply-To: <55075898-bf95-1805-3358-b0d1438feaa9@nsfocus.com>
Hi,
On 29. 07. 20, 9:53, 张云海 wrote:
> This patch dosen't fix the issue, the check should be in the loop.
>
> The change of the VT sze is before vgacon_scrollback_update, not in the
> meantime.
>
> Let's consider the following situation:
> suppose:
> vgacon_scrollback_cur->size is 65440
> vgacon_scrollback_cur->tail is 64960
> c->vc_size_row is 160
> count is 5
>
> Reset c->vc_size_row to 200 by VT_RESIZE, then call
> vgacon_scrollback_update.
>
> This will pass the check, since (vgacon_scrollback_cur->tail +
> c->vc_size_row)
> is 65160 which is less then vgacon_scrollback_cur->size(65440).
>
> However, in the 3rd iteration of the loop, vgacon_scrollback_cur->tail
> is update
> to 65360, the memcpy will overflow.
But the loop checks for the overflow:
if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
vgacon_scrollback_cur->tail = 0;
So the first 2 iterations would write to the end of the buffer and this
3rd one should have zeroed ->tail.
thanks,
--
js
suse labs
WARNING: multiple messages have this Message-ID (diff)
From: Jiri Slaby <jirislaby@kernel.org>
To: 张云海 <zhangyunhai@nsfocus.com>, b.zolnierkie@samsung.com
Cc: Security Officers <security@kernel.org>,
Kyungtae Kim <kt0755@gmail.com>,
Anthony Liguori <aliguori@amazon.com>, Greg KH <greg@kroah.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-fbdev@vger.kernel.org, linux-distros@vs.openwall.org,
Solar Designer <solar@openwall.com>,
Yang Yingliang <yangyingliang@huawei.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>
Subject: Re: [PATCH] vgacon: fix out of bounds write to the scrollback buffer
Date: Wed, 29 Jul 2020 10:11:57 +0200 [thread overview]
Message-ID: <c1f267aa-dfb3-91fa-3111-30c1676f1a91@kernel.org> (raw)
In-Reply-To: <55075898-bf95-1805-3358-b0d1438feaa9@nsfocus.com>
Hi,
On 29. 07. 20, 9:53, 张云海 wrote:
> This patch dosen't fix the issue, the check should be in the loop.
>
> The change of the VT sze is before vgacon_scrollback_update, not in the
> meantime.
>
> Let's consider the following situation:
> suppose:
> vgacon_scrollback_cur->size is 65440
> vgacon_scrollback_cur->tail is 64960
> c->vc_size_row is 160
> count is 5
>
> Reset c->vc_size_row to 200 by VT_RESIZE, then call
> vgacon_scrollback_update.
>
> This will pass the check, since (vgacon_scrollback_cur->tail +
> c->vc_size_row)
> is 65160 which is less then vgacon_scrollback_cur->size(65440).
>
> However, in the 3rd iteration of the loop, vgacon_scrollback_cur->tail
> is update
> to 65360, the memcpy will overflow.
But the loop checks for the overflow:
if (vgacon_scrollback_cur->tail >= vgacon_scrollback_cur->size)
vgacon_scrollback_cur->tail = 0;
So the first 2 iterations would write to the end of the buffer and this
3rd one should have zeroed ->tail.
thanks,
--
js
suse labs
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next prev parent reply other threads:[~2020-07-29 8:12 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200729070257eucas1p1f5841756104301e67907136e45d6e9f5@eucas1p1.samsung.com>
2020-07-29 7:02 ` [PATCH] vgacon: fix out of bounds write to the scrollback buffer Jiri Slaby
2020-07-29 7:02 ` Jiri Slaby
2020-07-29 7:02 ` Jiri Slaby
2020-07-29 7:53 ` 张云海
2020-07-29 7:53 ` 张云海
2020-07-29 7:53 ` 张云海
2020-07-29 8:11 ` Jiri Slaby [this message]
2020-07-29 8:11 ` Jiri Slaby
2020-07-29 8:11 ` Jiri Slaby
2020-07-29 8:19 ` 张云海
2020-07-29 8:19 ` 张云海
2020-07-29 8:19 ` 张云海
2020-07-29 11:20 ` Jiri Slaby
2020-07-29 11:20 ` Jiri Slaby
2020-07-29 11:20 ` Jiri Slaby
2020-07-29 13:37 ` Bartlomiej Zolnierkiewicz
2020-07-29 13:37 ` Bartlomiej Zolnierkiewicz
2020-07-29 13:37 ` Bartlomiej Zolnierkiewicz
[not found] <20200729130710.GA13262@openwall.com>
[not found] ` <b764c575-70be-80dd-6718-e84370a7b2b3@nsfocus.com>
2020-07-30 6:46 ` Jiri Slaby
2020-07-30 6:46 ` Jiri Slaby
2020-07-30 6:46 ` Jiri Slaby
2020-07-30 7:38 ` Jiri Slaby
2020-07-30 7:38 ` Jiri Slaby
2020-07-30 7:38 ` Jiri Slaby
2020-07-30 10:39 ` 张云海
2020-07-30 10:39 ` 张云海
2020-07-30 10:39 ` 张云海
2020-07-31 5:22 ` 张云海
2020-07-31 5:22 ` 张云海
2020-07-31 5:22 ` 张云海
2020-08-03 8:08 ` Jiri Slaby
2020-08-03 8:08 ` Jiri Slaby
2020-08-03 8:08 ` Jiri Slaby
2020-08-03 8:18 ` Greg KH
2020-08-03 8:18 ` Greg KH
2020-08-03 8:18 ` Greg KH
2020-08-03 8:45 ` Daniel Vetter
2020-08-03 8:45 ` Daniel Vetter
2020-08-03 8:45 ` Daniel Vetter
2020-08-03 9:47 ` Greg KH
2020-08-03 9:47 ` Greg KH
2020-08-03 9:47 ` Greg KH
2020-08-03 11:07 ` Bartlomiej Zolnierkiewicz
2020-08-03 11:07 ` Bartlomiej Zolnierkiewicz
2020-08-03 11:07 ` Bartlomiej Zolnierkiewicz
2020-08-04 7:37 ` Greg KH
2020-08-04 7:37 ` Greg KH
2020-08-04 7:37 ` Greg KH
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