Fix BZ #21654 - grp-merge.c alignment

[thirdparty/glibc.git] / grp / grp-merge.c

diff --git a/grp/grp-merge.c b/grp/grp-merge.c
index 0a1eb38d2c96bf7ad8f82c5668ac035512506b6a..6590e5d82350c08908dd8f1d71cb4a3a0a5ee9a5 100644 (file)
--- a/grp/grp-merge.c
+++ b/grp/grp-merge.c
@@ -1,5 +1,5 @@
 /* Group merging implementation.
-   Copyright (C) 2016 Free Software Foundation, Inc.
+   Copyright (C) 2016-2017 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -85,6 +85,14 @@ __copy_grp (const struct group srcgrp, const size_t buflen,
     }
   members[i] = NULL;
 
+  /* Align for pointers.  We can't simply align C because we need to
+     align destbuf[c].  */
+  if ((((uintptr_t)destbuf + c) & (__alignof__(char **) - 1)) != 0)
+    {
+      uintptr_t mis_align = ((uintptr_t)destbuf + c) & (__alignof__(char **) - 1);
+      c += __alignof__(char **) - mis_align;
+    }
+
   /* Copy the pointers from the members array into the buffer and assign them
      to the gr_mem member of destgrp.  */
   destgrp->gr_mem = (char **) &destbuf[c];
@@ -168,6 +176,14 @@ __merge_grp (struct group *savedgrp, char *savedbuf, char *savedend,
   /* Add the NULL-terminator.  */
   members[savedmemcount + memcount] = NULL;
 
+  /* Align for pointers.  We can't simply align C because we need to
+     align savedbuf[c].  */
+  if ((((uintptr_t)savedbuf + c) & (__alignof__(char **) - 1)) != 0)
+    {
+      uintptr_t mis_align = ((uintptr_t)savedbuf + c) & (__alignof__(char **) - 1);
+      c += __alignof__(char **) - mis_align;
+    }
+
   /* Copy the member array back into the buffer after the member list and free
      the member array.  */
   savedgrp->gr_mem = (char **) &savedbuf[c];