linux-kernel - [PATCH 2/2] net/netlabel: Avoid call to genlmsg

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Message-Id: <1296224232-8115-2-git-send-email-julia@diku.dk>
Date:	Fri, 28 Jan 2011 15:17:12 +0100
From:	Julia Lawall <julia@...u.dk>
To:	Paul Moore <paul.moore@...com>
Cc:	kernel-janitors@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] net/netlabel: Avoid call to genlmsg_cancel

genlmsg_cancel subtracts some constants from its second argument before
calling nlmsg_cancel.  nlmsg_cancel then calls nlmsg_trim on the same
arguments.  nlmsg_trim tests for NULL before doing any computation, but a
NULL second argument to genlmsg_cancel is no longer NULL due to the initial
subtraction.  Nothing else happens in this execution, so the call to
genlmsg_cancel is simply unnecessary in this case.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression data;
@@

if (data == NULL) { ...
* genlmsg_cancel(..., data);
  ...
  return ...;
}
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
 net/netlabel/netlabel_cipso_v4.c  |    2 +-
 net/netlabel/netlabel_mgmt.c      |    4 ++--
 net/netlabel/netlabel_unlabeled.c |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netlabel/netlabel_cipso_v4.c b/net/netlabel/netlabel_cipso_v4.c
index 5f14c84..0a1f77b 100644
--- a/net/netlabel/netlabel_cipso_v4.c
+++ b/net/netlabel/netlabel_cipso_v4.c
@@ -635,7 +635,7 @@ static int netlbl_cipsov4_listall_cb(struct cipso_v4_doi *doi_def, void *arg)
 			   cb_arg->seq, &netlbl_cipsov4_gnl_family,
 			   NLM_F_MULTI, NLBL_CIPSOV4_C_LISTALL);
 	if (data == NULL)
-		goto listall_cb_failure;
+		return ret_val;
 
 	ret_val = nla_put_u32(cb_arg->skb, NLBL_CIPSOV4_A_DOI, doi_def->doi);
 	if (ret_val != 0)
diff --git a/net/netlabel/netlabel_mgmt.c b/net/netlabel/netlabel_mgmt.c
index 998e85e..daaa01d 100644
--- a/net/netlabel/netlabel_mgmt.c
+++ b/net/netlabel/netlabel_mgmt.c
@@ -452,7 +452,7 @@ static int netlbl_mgmt_listall_cb(struct netlbl_dom_map *entry, void *arg)
 			   cb_arg->seq, &netlbl_mgmt_gnl_family,
 			   NLM_F_MULTI, NLBL_MGMT_C_LISTALL);
 	if (data == NULL)
-		goto listall_cb_failure;
+		return ret_val;
 
 	ret_val = netlbl_mgmt_listentry(cb_arg->skb, entry);
 	if (ret_val != 0)
@@ -617,7 +617,7 @@ static int netlbl_mgmt_protocols_cb(struct sk_buff *skb,
 			   &netlbl_mgmt_gnl_family, NLM_F_MULTI,
 			   NLBL_MGMT_C_PROTOCOLS);
 	if (data == NULL)
-		goto protocols_cb_failure;
+		return ret_val;
 
 	ret_val = nla_put_u32(skb, NLBL_MGMT_A_PROTOCOL, protocol);
 	if (ret_val != 0)
diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
index e2b0a68..b5d3945 100644
--- a/net/netlabel/netlabel_unlabeled.c
+++ b/net/netlabel/netlabel_unlabeled.c
@@ -1141,7 +1141,7 @@ static int netlbl_unlabel_staticlist_gen(u32 cmd,
 			   cb_arg->seq, &netlbl_unlabel_gnl_family,
 			   NLM_F_MULTI, cmd);
 	if (data == NULL)
-		goto list_cb_failure;
+		return ret_val;
 
 	if (iface->ifindex > 0) {
 		dev = dev_get_by_index(&init_net, iface->ifindex);

--
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