Source: @pullmoll
Upstream: no
Reason: errno=EFAULT when the address passed to mremap(2) is not valid

See Rich Felker's comment at https://www.openwall.com/lists/musl/2017/06/21/2 for
why we need to return errno as described in man mremap(2) from qemu-user-static.
Also speed up the loop when checking for increasing the mappings size to go
in steps of TARGET_PAGE_SIZE and OR-in a check for the very last byte of the range.
diff --git linux-user/mmap.c linux-user/mmap.c
index 7e3b245..1e8d0f1 100644
--- a/linux-user/mmap.c
+++ b/linux-user/mmap.c
@@ -738,7 +738,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
          !guest_range_valid_untagged(new_addr, new_size)) ||
         ((flags & MREMAP_MAYMOVE) == 0 &&
          !guest_range_valid_untagged(old_addr, new_size))) {
-        errno = ENOMEM;
+        errno = EFAULT;
         return -1;
     }
 
@@ -775,9 +775,10 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
             abi_ulong addr;
             for (addr = old_addr + old_size;
                  addr < old_addr + new_size;
-                 addr++) {
+                 addr += TARGET_PAGE_SIZE) {
                 prot |= page_get_flags(addr);
             }
+				prot |= page_get_flags(old_addr + new_size - 1);
         }
         if (prot == 0) {
             host_addr = mremap(g2h_untagged(old_addr),
@@ -796,7 +797,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
                 }
             }
         } else {
-            errno = ENOMEM;
+            errno = EFAULT;
             host_addr = MAP_FAILED;
         }
     }