[PATCH] fs: dlm: Protect IPV6 field access by CONFIG_IPV6

[Geert Uytterhoeven <geert@linux-m68k.org>]

If CONFIG_IPV6=n:

    In file included from fs/dlm/lowcomms.c:46:
    fs/dlm/lowcomms.c: In function ‘lowcomms_error_report’:
    ./include/net/sock.h:386:34: error: ‘struct sock_common’ has no member named ‘skc_v6_daddr’; did you mean ‘skc_daddr’?
      386 | #define sk_v6_daddr  __sk_common.skc_v6_daddr
	  |                                  ^~~~~~~~~~~~
    ./include/linux/printk.h:422:19: note: in expansion of macro ‘sk_v6_daddr’
      422 |   _p_func(_fmt, ##__VA_ARGS__);    \
	  |                   ^~~~~~~~~~~
    ./include/linux/printk.h:450:26: note: in expansion of macro ‘printk_index_wrap’
      450 | #define printk(fmt, ...) printk_index_wrap(_printk, fmt, ##__VA_ARGS__)
	  |                          ^~~~~~~~~~~~~~~~~
    ./include/linux/printk.h:644:3: note: in expansion of macro ‘printk’
      644 |   printk(fmt, ##__VA_ARGS__);    \
	  |   ^~~~~~
    fs/dlm/lowcomms.c:612:3: note: in expansion of macro ‘printk_ratelimited’
      612 |   printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
	  |   ^~~~~~~~~~~~~~~~~~

Fix this by protecting the code that accesses IPV6-only fields by a
check for CONFIG_IPV6.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Fixes: 4c3d90570bcc2b33 ("fs: dlm: don't call kernel_getpeername() in error_report()")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 fs/dlm/lowcomms.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 203470189011102d..f7fc1ac76ce83a5f 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -608,6 +608,7 @@ static void lowcomms_error_report(struct sock *sk)
 				   ntohs(inet->inet_dport), sk->sk_err,
 				   sk->sk_err_soft);
 		break;
+#if IS_ENABLED(CONFIG_IPV6)
 	case AF_INET6:
 		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
 				   "sending to node %d at %pI6c, "
@@ -616,6 +617,7 @@ static void lowcomms_error_report(struct sock *sk)
 				   ntohs(inet->inet_dport), sk->sk_err,
 				   sk->sk_err_soft);
 		break;
+#endif
 	default:
 		printk_ratelimited(KERN_ERR "dlm: node %d: socket error "
 				   "invalid socket family %d set, "
-- 
2.25.1