Messages in this thread | | | Date | Thu, 05 Jul 2018 22:52:04 -0700 | Subject | Re: [PATCH 4.14 14/61] vt: prevent leaking uninitialized data to userspace via /dev/vcs* | From | syzbot <> |
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> 4.14-stable review patch. If anyone has any objections, please let me > know.
> ------------------
> From: Alexander Potapenko <glider@google.com>
> 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 <glider@google.com> > Cc: stable <stable@vger.kernel.org> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> --- > 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.
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