This is another false positive in bad cast detection:

net/unix/af_unix.c: In function ‘unix_skb_scm_eq’:
net/unix/af_unix.c:1621:31: note: found mismatched rhs struct pointer types: 
‘struct unix_skb_parms’ and ‘char’

  const struct unix_skb_parms *u = &UNIXCB(skb);
                               ^

UNIXCB is:

        #define UNIXCB(skb)     (*(struct unix_skb_parms *)&((skb)->cb))

And ->cb is:

        char                    cb[48] __aligned(8);

This is a rather crazy cast, but appears to be safe in the face of
randomization, so whitelist it in the plugin.

Cc: Hannes Frederic Sowa <han...@stressinduktion.org>
Cc: Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 scripts/gcc-plugins/randomize_layout_plugin.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c 
b/scripts/gcc-plugins/randomize_layout_plugin.c
index e126ac7874af..bf110915a5aa 100644
--- a/scripts/gcc-plugins/randomize_layout_plugin.c
+++ b/scripts/gcc-plugins/randomize_layout_plugin.c
@@ -43,6 +43,8 @@ struct whitelist_entry {
 };
 
 static const struct whitelist_entry whitelist[] = {
+       /* unix_skb_parms via UNIXCB() buffer */
+       { "net/unix/af_unix.c", "unix_skb_parms", "char" },
        /* walk struct security_hook_heads as an array of struct list_head */
        { "security/security.c", "list_head", "security_hook_heads" },
        { }
-- 
2.7.4

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