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Message-ID: <nycvar.YSQ.7.76.1911051030580.30289@knanqh.ubzr>
Date: Tue, 5 Nov 2019 10:33:16 +0100 (CET)
From: Nicolas Pitre <nico@...xnic.net>
To: Jiri Slaby <jslaby@...e.com>
cc: Or Cohen <orcohen@...oaltonetworks.com>,
Greg KH <gregkh@...uxfoundation.org>, textshell@...uujin.de,
Daniel Vetter <daniel.vetter@...ll.ch>, sam@...nborg.org,
mpatocka@...hat.com, ghalat@...hat.com,
linux-kernel@...r.kernel.org, jwilk@...lk.net,
Nadav Markus <nmarkus@...oaltonetworks.com>,
syzkaller@...glegroups.com
Subject: Re: Bug report - slab-out-of-bounds in vcs_scr_readw
On Tue, 5 Nov 2019, Jiri Slaby wrote:
> Because unicode uses 4 bytes. The issue is that there is no handling for
> unicode in vcs_write at all. (Compare with vcs_read.)
Exact.
----- >8
Subject: [PATCH] vcs: prevent write access to vcsu devices
Commit d21b0be246bf ("vt: introduce unicode mode for /dev/vcs") guarded
against using devices containing attributes as this is not yet
implemented. It however failed to guard against writes to any devices
as this is also unimplemented.
Signed-off-by: Nicolas Pitre <npitre@...libre.com>
Cc: <stable@...r.kernel.org> # v4.19+
diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c
index fa07d79027..ef19b95b73 100644
--- a/drivers/tty/vt/vc_screen.c
+++ b/drivers/tty/vt/vc_screen.c
@@ -456,6 +456,9 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
size_t ret;
char *con_buf;
+ if (use_unicode(inode))
+ return -EOPNOTSUPP;
+
con_buf = (char *) __get_free_page(GFP_KERNEL);
if (!con_buf)
return -ENOMEM;
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