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render: Fix crash in RenderAddGlyphs (#23645) 

This patch fixes two bugs:
size is calculated as glyph height * padded_width. If the client submits
garbage, this may get above INT_MAX, resulting in a negative size if size is
unsigned. The sanity checks don't trigger for negative sizes and the server
goes and writes into random memory locations.

If the client submits glyphs with a width or height 0, the destination
pixmap is NULL, causing a null-pointer dereference. Since there's nothing to
composite if the width/height is 0, we might as well skip the whole thing
anyway.

Tested with Xvfb, Xephyr and Xorg.

X.Org Bug 23645 <http://bugs.freedesktop.org/show_bug.cgi?id=23645>

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Peter Hutterer 2009-10-01 10:03:42 +10:00
parent 758ab55d2d
commit 622fc98fd0
1 changed files with 5 additions and 1 deletions
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6
render/render.c
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@ -1043,7 +1043,7 @@ ProcRenderAddGlyphs (ClientPtr client)
CARD32 *gids;
xGlyphInfo *gi;
CARD8 *bits;
int size;
unsigned int size;
int err;
int i, screen;
PicturePtr pSrc = NULL, pDst = NULL;
@ -1131,6 +1131,10 @@ ProcRenderAddGlyphs (ClientPtr client)
ScreenPtr pScreen;
int error;
/* Skip work if it's invisibly small anyway */
if (!width || !height)
break;
pScreen = screenInfo.screens[screen];
pSrcPix = GetScratchPixmapHeader (pScreen,
width, height,