debian/patches/extra/0001-cirrus-fix-patterncopy-checks.patch

   1 From 391a9e6fd8c6cf615f2ffe44bb85245df52cc2b6 Mon Sep 17 00:00:00 2001
   2 From: Gerd Hoffmann <kraxel@redhat.com>
   3 Date: Thu, 9 Feb 2017 14:02:20 +0100
   4 Subject: [PATCH 1/2] cirrus: fix patterncopy checks
   5
   6 The blit_region_is_unsafe checks don't work correctly for the
   7 patterncopy source.  It's a fixed-sized region, which doesn't
   8 depend on cirrus_blt_{width,height}.  So go do the check in
   9 cirrus_bitblt_common_patterncopy instead, then tell blit_is_unsafe that
  10 it doesn't need to verify the source.  Also handle the case where we
  11 blit from cirrus_bitbuf correctly.
  12
  13 This patch replaces 5858dd1801883309bdd208d72ddb81c4e9fee30c.
  14
  15 Security impact:  I think for the most part error on the safe side this
  16 time, refusing blits which should have been allowed.
  17
  18 Only exception is placing the blit source at the end of the video ram,
  19 so cirrus_blt_srcaddr + 256 goes beyond the end of video memory.  But
  20 even in that case I'm not fully sure this actually allows read access to
  21 host memory.  To trick the commit 5858dd18 security checks one has to
  22 pick very small cirrus_blt_{width,height} values, which in turn implies
  23 only a fraction of the blit source will actually be used.
  24
  25 Cc: Wolfgang Bumiller <w.bumiller@proxmox.com>
  26 Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
  27 Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
  28 ---
  29  hw/display/cirrus_vga.c | 36 ++++++++++++++++++++++++++++++------
  30  1 file changed, 30 insertions(+), 6 deletions(-)
  31
  32 diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
  33 index 16f27e8..6bd13fc 100644
  34 --- a/hw/display/cirrus_vga.c
  35 +++ b/hw/display/cirrus_vga.c
  36 @@ -683,14 +683,39 @@ static void cirrus_invalidate_region(CirrusVGAState * s, int off_begin,
  37      }
  38  }
  39
  40 -static int cirrus_bitblt_common_patterncopy(CirrusVGAState * s,
  41 -                                           const uint8_t * src)
  42 +static int cirrus_bitblt_common_patterncopy(CirrusVGAState *s, bool videosrc)
  43  {
  44 +    uint32_t patternsize;
  45      uint8_t *dst;
  46 +    uint8_t *src;
  47
  48      dst = s->vga.vram_ptr + s->cirrus_blt_dstaddr;
  49
  50 -    if (blit_is_unsafe(s, false, true)) {
  51 +    if (videosrc) {
  52 +        switch (s->vga.get_bpp(&s->vga)) {
  53 +        case 8:
  54 +            patternsize = 64;
  55 +            break;
  56 +        case 15:
  57 +        case 16:
  58 +            patternsize = 128;
  59 +            break;
  60 +        case 24:
  61 +        case 32:
  62 +        default:
  63 +            patternsize = 256;
  64 +            break;
  65 +        }
  66 +        s->cirrus_blt_srcaddr &= ~(patternsize - 1);
  67 +        if (s->cirrus_blt_srcaddr + patternsize > s->vga.vram_size) {
  68 +            return 0;
  69 +        }
  70 +        src = s->vga.vram_ptr + s->cirrus_blt_srcaddr;
  71 +    } else {
  72 +        src = s->cirrus_bltbuf;
  73 +    }
  74 +
  75 +    if (blit_is_unsafe(s, true, true)) {
  76          return 0;
  77      }
  78
  79 @@ -731,8 +756,7 @@ static int cirrus_bitblt_solidfill(CirrusVGAState *s, int blt_rop)
  80
  81  static int cirrus_bitblt_videotovideo_patterncopy(CirrusVGAState * s)
  82  {
  83 -    return cirrus_bitblt_common_patterncopy(s, s->vga.vram_ptr +
  84 -                                            (s->cirrus_blt_srcaddr & ~7));
  85 +    return cirrus_bitblt_common_patterncopy(s, true);
  86  }
  87
  88  static int cirrus_do_copy(CirrusVGAState *s, int dst, int src, int w, int h)
  89 @@ -831,7 +855,7 @@ static void cirrus_bitblt_cputovideo_next(CirrusVGAState * s)
  90
  91      if (s->cirrus_srccounter > 0) {
  92          if (s->cirrus_blt_mode & CIRRUS_BLTMODE_PATTERNCOPY) {
  93 -            cirrus_bitblt_common_patterncopy(s, s->cirrus_bltbuf);
  94 +            cirrus_bitblt_common_patterncopy(s, false);
  95          the_end:
  96              s->cirrus_srccounter = 0;
  97              cirrus_bitblt_reset(s);
  98 --
  99 2.1.4
 100