[PATCH] Avoid capable() call in UNIX buffer check unless necessary

[Dan Smith]

As pointed out by Serge, we shouldn't call capable() unless we know we'll
need to exercise the ability.

Signed-off-by: Dan Smith <danms at us.ibm.com>
Cc: serue at us.ibm.com
---
 net/unix/checkpoint.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/net/unix/checkpoint.c b/net/unix/checkpoint.c
index 23040ce..55dfac1 100644
--- a/net/unix/checkpoint.c
+++ b/net/unix/checkpoint.c
@@ -278,9 +278,18 @@ static int sock_read_buffer_sendmsg(struct ckpt_ctx *ctx,
 		unix_sk(sk)->peer->sk_shutdown &= ~SHUTDOWN_MASK;
 	}
 
-	/* Make sure there's room in the send buffer */
+	/* Make sure there's room in the send buffer: Worst case, we
+	 * give them the benefit of the doubt and set the buffer limit
+	 * to the system default.  This should cover the case where
+	 * the user set the limit low after loading up the buffer.
+	 *
+	 * However, if there isn't room in the buffer and the system
+	 * default won't accommodate them either, then increase the
+	 * limit as needed, only if they have CAP_NET_ADMIN.
+	 */
 	sndbuf = sk->sk_sndbuf;
 	if (((sk->sk_sndbuf - atomic_read(&sk->sk_wmem_alloc)) < h->lin_len) &&
+	    (h->lin_len > sysctl_wmem_max) &&
 	    capable(CAP_NET_ADMIN))
 		sk->sk_sndbuf += h->lin_len;
 	else
-- 
1.6.2.5