mm: Enforce VM_IOREMAP flag and range in ioremap_page_range.

There are various users of get_vm_area() + ioremap_page_range() APIs.
Enforce that get_vm_area() was requested as VM_IOREMAP type and range
passed to ioremap_page_range() matches created vm_area to avoid
accidentally ioremap-ing into wrong address range.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/bpf/20240305030516.41519-2-alexei.starovoitov@gmail.com

mm/vmalloc.c

@@ -307,8 +307,21 @@ static int vmap_range_noflush(unsigned long addr, unsigned long end,
 int ioremap_page_range(unsigned long addr, unsigned long end,
 		phys_addr_t phys_addr, pgprot_t prot)
 {
+	struct vm_struct *area;
 	int err;
 
+	area = find_vm_area((void *)addr);
+	if (!area || !(area->flags & VM_IOREMAP)) {
+		WARN_ONCE(1, "vm_area at addr %lx is not marked as VM_IOREMAP\n", addr);
+		return -EINVAL;
+	}
+	if (addr != (unsigned long)area->addr ||
+	    (void *)end != area->addr + get_vm_area_size(area)) {
+		WARN_ONCE(1, "ioremap request [%lx,%lx) doesn't match vm_area [%lx, %lx)\n",
+			  addr, end, (long)area->addr,
+			  (long)area->addr + get_vm_area_size(area));
+		return -ERANGE;
+	}
 	err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot),
 				 ioremap_max_page_shift);
 	flush_cache_vmap(addr, end);