drm/nouveau: fix u32 overflow in pushbuf reloc bounds check

nouveau_gem_pushbuf_reloc_apply() validates each relocation with

    if (r->reloc_bo_offset + 4 > nvbo->bo.base.size)

but reloc_bo_offset is __u32 (uapi/drm/nouveau_drm.h) and the integer
literal 4 promotes to unsigned int, so the addition is performed in 32
bits and wraps before the comparison against the size_t bo size.

Cast to u64 so the addition happens in 64-bit arithmetic.

Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Simona Vetter <simona@ffwll.ch>
Reported-by: Anthropic
Cc: stable <stable@kernel.org>
Assisted-by: gkh_clanker_t1000
Fixes: a1606a9 ("drm/nouveau: new gem pushbuf interface, bump to 0.0.16")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Add Fixes: tag. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: gregkh

drivers/gpu/drm/nouveau/nouveau_gem.c

@@ -686,7 +686,7 @@ nouveau_gem_pushbuf_reloc_apply(struct nouveau_cli *cli,
 		}
 		nvbo = (void *)(unsigned long)bo[r->reloc_bo_index].user_priv;
 
-		if (unlikely(r->reloc_bo_offset + 4 >
+		if (unlikely((u64)r->reloc_bo_offset + 4 >
 			     nvbo->bo.base.size)) {
 			NV_PRINTK(err, cli, "reloc outside of bo\n");
 			ret = -EINVAL;