Commit 9a98e7a8 authored Mar 28, 2020 by Nicolas Pitre Committed by Greg Kroah-Hartman Apr 23, 2020

vt: don't use kmalloc() for the unicode screen buffer



Even if the actual screen size is bounded in vc_do_resize(), the unicode
buffer is still a little more than twice the size of the glyph buffer
and may exceed MAX_ORDER down the kmalloc() path. This can be triggered
from user space.

Since there is no point having a physically contiguous buffer here,
let's avoid the above issue as well as reducing pressure on high order
allocations by using vmalloc() instead.

Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Cc: <stable@vger.kernel.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://lore.kernel.org/r/nycvar.YSQ.7.76.2003282214210.2671@knanqh.ubzr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 66bb1c95

drivers/tty/vt/vt.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -81,6 +81,7 @@
		#include <linux/errno.h>
		#include <linux/kd.h>
		#include <linux/slab.h>
		#include <linux/vmalloc.h>
		#include <linux/major.h>
		#include <linux/mm.h>
		#include <linux/console.h>
		@@ -350,7 +351,7 @@ static struct uni_screen *vc_uniscr_alloc(unsigned int cols, unsigned int rows)
		/* allocate everything in one go */
		memsize = cols * rows * sizeof(char32_t);
		memsize += rows * sizeof(char32_t *);
		p = kmalloc(memsize, GFP_KERNEL);
		p = vmalloc(memsize);
		if (!p)
		return NULL;

		@@ -366,7 +367,7 @@ static struct uni_screen *vc_uniscr_alloc(unsigned int cols, unsigned int rows)

		static void vc_uniscr_set(struct vc_data vc, struct uni_screen new_uniscr)
		{
		kfree(vc->vc_uni_screen);
		vfree(vc->vc_uni_screen);
		vc->vc_uni_screen = new_uniscr;
		}

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