fix mremap-underflow.diff

Author: marler8997

patch/mremap-underflow.diff

@@ -2,13 +2,12 @@ diff --git a/linux-user/mmap.c b/linux-user/mmap.c
 index e378033797..da0fe4cc86 100644
 --- a/linux-user/mmap.c
 +++ b/linux-user/mmap.c
-@@ -708,7 +708,8 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
+@@ -708,7 +708,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
          if (prot == 0) {
              host_addr = mremap(g2h(old_addr), old_size, new_size, flags);
              if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) {
 -                mmap_reserve(old_addr + old_size, new_size - old_size);
-+                if (new_size > old_size)
-+                    mmap_reserve(old_addr + old_size, new_size - old_size);
++                mmap_reserve(old_addr + old_size, old_size - new_size);
              }
          } else {
              errno = ENOMEM;