CVE-2026-80700drm/vmwgfx: validate external BO copy bounds for both stride paths

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4e0f669e2951b742239c6fe847fcc406fe78748d
• https://git.kernel.org/stable/c/e7b25a6011781ebfdbc458552cae6d4156732771
• https://git.kernel.org/stable/c/042ca38779554687fc32b66a28328e0d9a36c58f
• https://git.kernel.org/stable/c/5e4a2d15637a906cbd9bc98e0bf969f5f713e344
• https://git.kernel.org/stable/c/706c93c5813caabbb0d0a576c017d15aeec2c113