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

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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>
This commit is contained in:
Nicolas Pitre 2020-03-28 22:25:11 -04:00 committed by Greg Kroah-Hartman
parent 66bb1c9518
commit 9a98e7a80f
1 changed files with 3 additions and 2 deletions

5
drivers/tty/vt/vt.c

@ -81,6 +81,7 @@
#include <linux/errno.h> #include <linux/errno.h>
#include <linux/kd.h> #include <linux/kd.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/major.h> #include <linux/major.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/console.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 */ /* allocate everything in one go */
memsize = cols * rows * sizeof(char32_t); memsize = cols * rows * sizeof(char32_t);
memsize += rows * sizeof(char32_t *); memsize += rows * sizeof(char32_t *);
p = kmalloc(memsize, GFP_KERNEL); p = vmalloc(memsize);
if (!p) if (!p)
return NULL; 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) 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; vc->vc_uni_screen = new_uniscr;
} }