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cirrus: add blit_is_unsafe call to cirrus_bitblt_cputovideo (CVE-2017-2620) 

CIRRUS_BLTMODE_MEMSYSSRC blits do NOT check blit destination
and blit width, at all.  Oops.  Fix it.

Security impact: high.

The missing blit destination check allows to write to host memory.
Basically same as CVE-2014-8106 for the other blit variants.

Cc: qemu-stable@nongnu.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Gerd Hoffmann 2017-02-08 11:18:36 +01:00
parent 10f25e4844
commit 92f2b88cea
1 changed files with 8 additions and 0 deletions
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8
hw/display/cirrus_vga.c
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@ -900,6 +900,10 @@ static int cirrus_bitblt_cputovideo(CirrusVGAState * s)
{ {
int w; int w;
if (blit_is_unsafe(s, true)) {
return 0;
}
s->cirrus_blt_mode &= ~CIRRUS_BLTMODE_MEMSYSSRC; s->cirrus_blt_mode &= ~CIRRUS_BLTMODE_MEMSYSSRC;
s->cirrus_srcptr = &s->cirrus_bltbuf[0]; s->cirrus_srcptr = &s->cirrus_bltbuf[0];
s->cirrus_srcptr_end = &s->cirrus_bltbuf[0]; s->cirrus_srcptr_end = &s->cirrus_bltbuf[0];
@ -925,6 +929,10 @@ static int cirrus_bitblt_cputovideo(CirrusVGAState * s)
} }
s->cirrus_srccounter = s->cirrus_blt_srcpitch * s->cirrus_blt_height; s->cirrus_srccounter = s->cirrus_blt_srcpitch * s->cirrus_blt_height;
} }
/* the blit_is_unsafe call above should catch this */
assert(s->cirrus_blt_srcpitch <= CIRRUS_BLTBUFSIZE);
s->cirrus_srcptr = s->cirrus_bltbuf; s->cirrus_srcptr = s->cirrus_bltbuf;
s->cirrus_srcptr_end = s->cirrus_bltbuf + s->cirrus_blt_srcpitch; s->cirrus_srcptr_end = s->cirrus_bltbuf + s->cirrus_blt_srcpitch;
cirrus_update_memory_access(s); cirrus_update_memory_access(s);