Author: gordon
Date: Wed Apr 4 05:21:46 2018
New Revision: 331981
URL: https://svnweb.freebsd.org/changeset/base/331981
Log:
Limit glyph count in vtfont_load to avoid integer overflow.
Invalid font data passed to PIO_VFONT can result in an integer overflow
in glyphsize. Characters may then be drawn on the console using glyph
map entries that point beyond the end of allocated glyph memory,
resulting in a kernel memory disclosure.
Submitted by: emaste
Reported by: Dr. Silvio Cesare of InfoSect
Security: CVE-2018-6917
Security: FreeBSD-SA-18:04.vt
Sponsored by: The FreeBSD Foundation
Modified:
head/sys/dev/vt/vt_font.c
Modified: head/sys/dev/vt/vt_font.c
==============================================================================
--- head/sys/dev/vt/vt_font.c Wed Apr 4 04:26:21 2018 (r331980)
+++ head/sys/dev/vt/vt_font.c Wed Apr 4 05:21:46 2018 (r331981)
@@ -44,6 +44,7 @@ static MALLOC_DEFINE(M_VTFONT, "vtfont", "vt font");
/* Some limits to prevent abnormal fonts from being loaded. */
#define VTFONT_MAXMAPPINGS 65536
+#define VTFONT_MAXGLYPHS 131072
#define VTFONT_MAXGLYPHSIZE 2097152
#define VTFONT_MAXDIMENSION 128
@@ -173,7 +174,8 @@ vtfont_load(vfnt_t *f, struct vt_font **ret)
/* Make sure the dimensions are valid. */
if (f->width < 1 || f->height < 1)
return (EINVAL);
- if (f->width > VTFONT_MAXDIMENSION || f->height > VTFONT_MAXDIMENSION)
+ if (f->width > VTFONT_MAXDIMENSION || f->height > VTFONT_MAXDIMENSION ||
+ f->glyph_count > VTFONT_MAXGLYPHS)
return (E2BIG);
/* Not too many mappings. */
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