[PATCH v4 bpf-next 1/2] mm: Enforce VM_IOREMAP flag and range in ioremap_page_range.

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

From: Alexei Starovoitov <ast@xxxxxxxxxx>

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.

Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
 mm/vmalloc.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d12a17fc0c17..f42f98a127d5 100644
--- a/mm/vmalloc.c
+++ b/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);
-- 
2.43.0