linux-kernel - [PATCH 1/4 v2] mtd: brcmnand: improve memory management

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Date:	Thu, 19 Nov 2015 22:32:15 +0100 (CET)
From:	Julia Lawall <julia.lawall@...6.fr>
To:	Brian Norris <computersforpeace@...il.com>
cc:	kernel-janitors@...r.kernel.org,
	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org,
	bcm-kernel-feedback-list@...adcom.com,
	linux-kernel@...r.kernel.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Andrew Lunn <andrew@...n.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jason Cooper <jason@...edaemon.net>,
	Kamal Dasu <kdasu.kdev@...il.com>
Subject: [PATCH 1/4 v2] mtd: brcmnand: improve memory management

This patch addresses two related memory management issues in the probe
function:

1. for_each_available_child_of_node performs an of_node_get on each
iteration, so a break out of the loop requires an of_node_put.

A simplified version of the semantic patch that fixes this problem is as
follows (http://coccinelle.lip6.fr):

// <smpl>
@@
expression root,e;
local idexpression child;
@@

 for_each_available_child_of_node(root, child) {
   ... when != of_node_put(child)
       when != e = child
(
   return child;
|
+  of_node_put(child);
?  return ...;
)
   ...
 }
// </smpl>

2. The devm_kzalloc'd data is not used if brcmnand_init_cs fails.  Free it
immediately, using devm_kfree in this case, instead of waiting for the
remove function.

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

---

v2: Drop of_node_get addition, as another patch will get rid of the need
for it completely.

 drivers/mtd/nand/brcmnand/brcmnand.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
index 2a437c7..551d474 100644
--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -2237,15 +2237,19 @@ int brcmnand_probe(struct platform_device *pdev, struct brcmnand_soc *soc)
 			struct brcmnand_host *host;
 
 			host = devm_kzalloc(dev, sizeof(*host), GFP_KERNEL);
-			if (!host)
+			if (!host) {
+				of_node_put(child);
 				return -ENOMEM;
+			}
 			host->pdev = pdev;
 			host->ctrl = ctrl;
 			host->of_node = child;
 
 			ret = brcmnand_init_cs(host);
-			if (ret)
+			if (ret) {
+				devm_kfree(dev, host);
 				continue; /* Try all chip-selects */
+			}
 
 			list_add_tail(&host->node, &ctrl->host_list);
 		}
--
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