From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f69.google.com ([209.85.166.69]:41094 "EHLO mail-io1-f69.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730863AbeKLFsf (ORCPT ); Mon, 12 Nov 2018 00:48:35 -0500 Received: by mail-io1-f69.google.com with SMTP id k3-v6so7974848ioq.8 for ; Sun, 11 Nov 2018 11:59:08 -0800 (PST) MIME-Version: 1.0 Date: Sun, 11 Nov 2018 11:59:07 -0800 In-Reply-To: Message-ID: <000000000000687eda057a6904e9@google.com> Subject: Re: [PATCH 3.16 213/366] vt: prevent leaking uninitialized data to userspace via /dev/vcs* From: syzbot To: Ben Hutchings Cc: akpm@linux-foundation.org, ben@decadent.org.uk, glider@google.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: stable-owner@vger.kernel.org List-ID: > 3.16.61-rc1 review patch. If anyone has any objections, please let me > know. > ------------------ > From: Alexander Potapenko > commit 21eff69aaaa0e766ca0ce445b477698dc6a9f55a upstream. > KMSAN reported an infoleak when reading from /dev/vcs*: > BUG: KMSAN: kernel-infoleak in vcs_read+0x18ba/0x1cc0 > Call Trace: > ... > kmsan_copy_to_user+0x7a/0x160 mm/kmsan/kmsan.c:1253 > copy_to_user ./include/linux/uaccess.h:184 > vcs_read+0x18ba/0x1cc0 drivers/tty/vt/vc_screen.c:352 > __vfs_read+0x1b2/0x9d0 fs/read_write.c:416 > vfs_read+0x36c/0x6b0 fs/read_write.c:452 > ... > Uninit was created at: > kmsan_save_stack_with_flags mm/kmsan/kmsan.c:279 > kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:189 > kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:315 > __kmalloc+0x13a/0x350 mm/slub.c:3818 > kmalloc ./include/linux/slab.h:517 > vc_allocate+0x438/0x800 drivers/tty/vt/vt.c:787 > con_install+0x8c/0x640 drivers/tty/vt/vt.c:2880 > tty_driver_install_tty drivers/tty/tty_io.c:1224 > tty_init_dev+0x1b5/0x1020 drivers/tty/tty_io.c:1324 > tty_open_by_driver drivers/tty/tty_io.c:1959 > tty_open+0x17b4/0x2ed0 drivers/tty/tty_io.c:2007 > chrdev_open+0xc25/0xd90 fs/char_dev.c:417 > do_dentry_open+0xccc/0x1440 fs/open.c:794 > vfs_open+0x1b6/0x2f0 fs/open.c:908 > ... > Bytes 0-79 of 240 are uninitialized > Consistently allocating |vc_screenbuf| with kzalloc() fixes the problem > Reported-by: syzbot+17a8efdf800000@syzkaller.appspotmail.com > Signed-off-by: Alexander Potapenko > Signed-off-by: Greg Kroah-Hartman > Signed-off-by: Ben Hutchings > --- > drivers/tty/vt/vt.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > --- a/drivers/tty/vt/vt.c > +++ b/drivers/tty/vt/vt.c > @@ -782,7 +782,7 @@ int vc_allocate(unsigned int currcons) / > if (!*vc->vc_uni_pagedir_loc) > con_set_default_unimap(vc); > - vc->vc_screenbuf = kmalloc(vc->vc_screenbuf_size, GFP_KERNEL); > + vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_KERNEL); > if (!vc->vc_screenbuf) > goto err_free; > @@ -869,7 +869,7 @@ static int vc_do_resize(struct tty_struc > if (new_screen_size > (4 << 20)) > return -EINVAL; > - newscreen = kmalloc(new_screen_size, GFP_USER); > + newscreen = kzalloc(new_screen_size, GFP_USER); > if (!newscreen) > return -ENOMEM; Can't find the corresponding bug.