From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Frediano Ziglio <fziglio@redhat.com>

Date: Tue, 8 Sep 2015 10:13:24 +0100

Subject: [PATCH] Fix integer overflow computing glyph_size in red_get_string

If bpp is int the formula can lead to weird overflows. width and height

are uint16_t so the formula is:

  size_t = u16 * (u16 * int + const_int) / const_int;

so it became

  size_t = (int) u16 * ((int) u16 * int + const_int) / const_int;

However the (int) u16 * (int) u16 can then became negative to overflow.

Under 64 bit architectures size_t is 64 and int usually 32 so converting

this negative 32 bit number to a unsigned 64 bit lead to a very big

number as the signed is extended and then converted to unsigned.

Using unsigned arithmetic prevent extending the sign.

Signed-off-by: Frediano Ziglio <fziglio@redhat.com>

Acked-by: Christophe Fergeau <cfergeau@redhat.com>

---

 server/red_parse_qxl.c | 8 +++++---

 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/server/red_parse_qxl.c b/server/red_parse_qxl.c

index 2d4636e..c4b82be 100644

--- a/server/red_parse_qxl.c

+++ b/server/red_parse_qxl.c

@@ -807,7 +807,9 @@ static SpiceString *red_get_string(RedMemSlotInfo *slots, int group_id,

     uint8_t *data;

     bool free_data;

     size_t chunk_size, qxl_size, red_size, glyph_size;

-    int glyphs, bpp = 0, i;

+    int glyphs, i;

+    /* use unsigned to prevent integer overflow in multiplication below */

+    unsigned int bpp = 0;

     int error;

     uint16_t qxl_flags, qxl_length;

@@ -846,7 +848,7 @@ static SpiceString *red_get_string(RedMemSlotInfo *slots, int group_id,

     while (start < end) {

         spice_assert((QXLRasterGlyph*)(&start->data[0]) <= end);

         glyphs++;

-        glyph_size = start->height * ((start->width * bpp + 7) / 8);

+        glyph_size = start->height * ((start->width * bpp + 7u) / 8u);

         red_size += sizeof(SpiceRasterGlyph *) + SPICE_ALIGN(sizeof(SpiceRasterGlyph) + glyph_size, 4);

         start = (QXLRasterGlyph*)(&start->data[glyph_size]);

     }

@@ -867,7 +869,7 @@ static SpiceString *red_get_string(RedMemSlotInfo *slots, int group_id,

         glyph->height = start->height;

         red_get_point_ptr(&glyph->render_pos, &start->render_pos);

         red_get_point_ptr(&glyph->glyph_origin, &start->glyph_origin);

-        glyph_size = glyph->height * ((glyph->width * bpp + 7) / 8);

+        glyph_size = glyph->height * ((glyph->width * bpp + 7u) / 8u);

         spice_assert((QXLRasterGlyph*)(&start->data[glyph_size]) <= end);

         memcpy(glyph->data, start->data, glyph_size);

         start = (QXLRasterGlyph*)(&start->data[glyph_size]);