drm/amdgpu: check num_entries in GEM_OP GET_MAPPING_INFO

drm/amdgpu: check num_entries in GEM_OP GET_MAPPING_INFO

kvcalloc(args->num_entries, sizeof(*vm_entries), GFP_KERNEL) at
amdgpu_gem.c:1050 uses the user-supplied num_entries directly without
any upper bounds check. Since num_entries is a __u32 and
sizeof(drm_amdgpu_gem_vm_entry) is 32 bytes, a large num_entries
produces an allocation exceeding INT_MAX, triggering
WARNING in __kvmalloc_node_noprof(), causing a kernel WARNING,
TAINT_WARN, and panic on CONFIG_PANIC_ON_WARN=y systems.

Add a size bounds check before we invoke the kvzalloc() to
reject oversized num_entries early with -EINVAL.

Fixes: 4d82724f7f2b ("drm/amdgpu: Add mapping info option for GEM_OP ioctl")
Signed-off-by: Ziyi Guo <n7l8m4@u.northwestern.edu>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 1fe7bf5457f6efd7be60b17e23163ba54341d73d)
Cc: stable@vger.kernel.org