linux-kernel - [PATCH 1/6] drivers/pci/hotplug/cpci_hotplug_core.c: ensure a consistent return value in error case

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Date:	Sat, 14 Jul 2012 18:43:03 +0200
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Scott Murray <scott@...teful.org>
Cc:	kernel-janitors@...r.kernel.org,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] drivers/pci/hotplug/cpci_hotplug_core.c: ensure a consistent return value in error case

From: Julia Lawall <Julia.Lawall@...6.fr>

Typically, the return value desired for the failure of a function with an
integer return value is a negative integer.  In these cases, the return
value is sometimes a negative integer and sometimes 0, due to a subsequent
initialization of the return variable within the loop.

A simplified version of the semantic match that finds this problem is:
(http://coccinelle.lip6.fr/)

//<smpl>
@r exists@
identifier ret;
position p;
constant C;
expression e1,e3,e4;
statement S;
@@

ret = -C
... when != ret = e3
    when any
if@p (...) S
... when any
if (\(ret != 0\|ret < 0\|ret > 0\) || ...) { ... return ...; }
... when != ret = e3
    when any
*if@p (...)
{
  ... when != ret = e4
  return ret;
}
//</smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
 drivers/pci/hotplug/cpci_hotplug_core.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/hotplug/cpci_hotplug_core.c b/drivers/pci/hotplug/cpci_hotplug_core.c
index 3fadf2f..2b4c412 100644
--- a/drivers/pci/hotplug/cpci_hotplug_core.c
+++ b/drivers/pci/hotplug/cpci_hotplug_core.c
@@ -225,7 +225,7 @@ cpci_hp_register_bus(struct pci_bus *bus, u8 first, u8 last)
 	struct hotplug_slot *hotplug_slot;
 	struct hotplug_slot_info *info;
 	char name[SLOT_NAME_SIZE];
-	int status = -ENOMEM;
+	int status;
 	int i;
 
 	if (!(controller && bus))
@@ -237,18 +237,24 @@ cpci_hp_register_bus(struct pci_bus *bus, u8 first, u8 last)
 	 */
 	for (i = first; i <= last; ++i) {
 		slot = kzalloc(sizeof (struct slot), GFP_KERNEL);
-		if (!slot)
+		if (!slot) {
+			status = -ENOMEM;
 			goto error;
+		}
 
 		hotplug_slot =
 			kzalloc(sizeof (struct hotplug_slot), GFP_KERNEL);
-		if (!hotplug_slot)
+		if (!hotplug_slot) {
+			status = -ENOMEM;
 			goto error_slot;
+		}
 		slot->hotplug_slot = hotplug_slot;
 
 		info = kzalloc(sizeof (struct hotplug_slot_info), GFP_KERNEL);
-		if (!info)
+		if (!info) {
+			status = -ENOMEM;
 			goto error_hpslot;
+		}
 		hotplug_slot->info = info;
 
 		slot->bus = bus;

--
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