This is a note to let you know that I've just added the patch titled
vt: prevent leaking uninitialized data to userspace via /dev/vcs*
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From 21eff69aaaa0e766ca0ce445b477698dc6a9f55a Mon Sep 17 00:00:00 2001
From: Alexander Potapenko <glider@xxxxxxxxxx>
Date: Thu, 14 Jun 2018 12:23:09 +0200
Subject: vt: prevent leaking uninitialized data to userspace via /dev/vcs*
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/vt/vt.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 1eb1a376a041..15eb6c829d39 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -784,7 +784,7 @@ int vc_allocate(unsigned int currcons) /* return 0 on success */
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;
@@ -871,7 +871,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
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;
--
2.18.0
