In the Linux kernel, the following vulnerability has been resolved: drm/vmwgfx: Prevent unmapping active read buffers The kms paths keep a persistent map active to read and compare the cursor buffer. These maps can race with each other in simple scenario where: a) buffer "a" mapped for update b) buffer "a" mapped for compare c) do the compare d) unmap "a" for compare e) update the cursor f) unmap "a" for update At step "e" the buffer has been unmapped and the read contents is bogus. Prevent unmapping of active read buffers by simply keeping a count of how many paths have currently active maps and unmap only when the count reaches 0.
https://git.kernel.org/stable/c/d5228d158e4c0b1663b3983044913c15c3d0135e
https://git.kernel.org/stable/c/aba07b9a0587f50e5d3346eaa19019cf3f86c0ea
https://git.kernel.org/stable/c/58a3714db4d9dcaeb9fc4905141e17b9f536c0a5
https://git.kernel.org/stable/c/0851b1ec650adadcaa23ec96daad95a55bf966f0