CVE-2026-80700

In the Linux kernel, the following vulnerability has been resolved:

drm/vmwgfx: validate external BO copy bounds for both stride paths

vmw_external_bo_copy() trusts caller-supplied offsets, strides, and

heights and operates on imported dma-buf vmaps:

- The equal-stride memcpy() bound was clamped after subtracting the

offsets from dst_size and src_size; an offset larger than the BO

size wraps the unsigned subtraction to a huge value and the

resulting memcpy() runs off the end of the vmap. dst_stride *

height is also a u32 multiplication that can overflow.

- The non-equal-stride row-by-row path had no bound at all. The

loop touches bytes through offset + (height - 1) * stride +

width_in_bytes, with only a WARN_ON(dst_stride < width_in_bytes),

and could likewise step past the end of either mapping.

The offsets and strides are derived from STDU/SOU plane state, so a

configured CRTC submitting a crafted atomic commit on an imported

framebuffer can reach this path.

Validate the exact row-copy endpoint against each BO's size up front

using check_mul_overflow() and check_add_overflow(). Use the bulk

memcpy() path only when width_in_bytes covers the whole stride;

otherwise copy one row at a time so partial-row updates near the bottom

of a framebuffer remain valid. Also reject zero strides and stride <

width_in_bytes, both of which the row-by-row path cannot represent

safely.