drm/tests: shmem: Hold reservation lock around madvise

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/tests: shmem: Hold reservation lock around madvise Acquire and release the GEM object's reservation lock around calls to the object's madvide operation. The tests use drm_gem_shmem_madvise_locked(), which led to errors such as show below. [ 58.339389] WARNING: CPU: 1 PID: 1352 at drivers/gpu/drm/drm_gem_shmem_helper.c:499 drm_gem_shmem_madvise_locked+0xde/0x140 Only export the new helper drm_gem_shmem_madvise() for Kunit tests. This is not an interface for regular drivers.

References

• https://git.kernel.org/stable/c/9cc77691b5fd615625955cedf726da57543088f1
• https://git.kernel.org/stable/c/07cfcab370da06f26c273306571cbb0bfa3b9c52
• https://git.kernel.org/stable/c/607d07d8cc0b835a8701259f08a03dc149b79b4f