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[PR #3994] [PR #3993] glamor: size tmp_bits buffer for source coordinate range in upload_boxes

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glamor_upload_boxes() allocates the tmp_bits buffer (used for 24-bit to
32-bit depth conversion) based on the destination pixmap height, but
indexes it using source coordinates (y1 - dy_dst + dy_src). When the
source is taller than the destination, the source-relative offset
exceeds the destination height, causing writes past the buffer end.

Size the buffer to account for the source coordinate mapping:
byte_stride * (pixmap->drawable.height - dy_dst + dy_src). This
ensures the buffer covers the full range of source rows that will be
accessed during the upload.

This vulnerability was discovered by:
  Anonymous working with TrendAI Zero Day Initiative

ZDI-CAN-32361

CVE-2026-93522

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Assisted-by: Claude:claude-opus-4-6
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2341>
(cherry picked from commit ad26c26bf7)
PR: https://github.com/X11Libre/xserver/pull/3993
PR: https://github.com/X11Libre/xserver/pull/3994
This commit is contained in:
Peter Hutterer 2026-08-26 17:17:21 +10:00 • committed by Enrico Weigelt, metux IT consult
commit 518f162e9e
1 changed files with 8 additions and 2 deletions
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10
glamor/glamor_transfer.c
View file

@ -46,8 +46,14 @@ glamor_upload_boxes(DrawablePtr drawable, BoxPtr in_boxes, int in_nbox,
int bytes_per_pixel = PICT_FORMAT_BPP(f->render_format) >> 3;
char *tmp_bits = NULL;
if (glamor_drawable_effective_depth(drawable) == 24 && pixmap->drawable.depth == 32)
tmp_bits = XNFalloc(byte_stride * pixmap->drawable.height);
if (glamor_drawable_effective_depth(drawable) == 24 && pixmap->drawable.depth == 32) {
int tmp_height = pixmap->drawable.height - dy_dst + dy_src;
if (tmp_height > 0) {
if (byte_stride > 0 && tmp_height > INT_MAX / byte_stride)
return;
tmp_bits = XNFalloc(byte_stride * tmp_height);
}
}
glamor_make_current(glamor_priv);