patch "vt: don't hardcode the mem allocation upper bound" added to tty-linus

patch "vt: don't hardcode the mem allocation upper bound" added to tty-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    vt: don't hardcode the mem allocation upper bound

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 2717769e204e83e65b8819c5e2ef3e5b6639b270 Mon Sep 17 00:00:00 2001
From: Nicolas Pitre <nico@fluxnic.net>
Date: Sat, 28 Mar 2020 17:32:42 -0400
Subject: vt: don't hardcode the mem allocation upper bound

The code in vc_do_resize() bounds the memory allocation size to avoid
exceeding MAX_ORDER down the kzalloc() call chain and generating a
runtime warning triggerable from user space. However, not only is it
unwise to use a literal value here, but MAX_ORDER may also be
configurable based on CONFIG_FORCE_MAX_ZONEORDER.
Let's use KMALLOC_MAX_SIZE instead.

Note that prior commit bb1107f7c605 ("mm, slab: make sure that
KMALLOC_MAX_SIZE will fit into MAX_ORDER") the KMALLOC_MAX_SIZE value
could not be relied upon.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Cc: <stable@vger.kernel.org> # v4.10+

Link: https://lore.kernel.org/r/nycvar.YSQ.7.76.2003281702410.2671@knanqh.ubzr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/vt/vt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 3272759b1f3c..e5ffed795e4c 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1207,7 +1207,7 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,
 	if (new_cols == vc->vc_cols && new_rows == vc->vc_rows)
 		return 0;
 
-	if (new_screen_size > (4 << 20))
+	if (new_screen_size > KMALLOC_MAX_SIZE)
 		return -EINVAL;
 	newscreen = kzalloc(new_screen_size, GFP_USER);
 	if (!newscreen)
-- 
2.26.2