Subject: [PATCH v3] of: fix memory leak related to safe_name()

From: Frank Rowand <[email-masked]>
Date: Thu, 16 Jun 2016 10:51:46 -0700

From: Frank Rowand <[email-masked]>

Fix a memory leak resulting from memory allocation in safe_name().
This patch fixes all call sites of safe_name().

Mathieu Malaterre reported the memory leak on boot:

On my PowerMac device-tree would generate a duplicate name:

[    0.023043] device-tree: Duplicate name in PowerPC,G4@0, renamed to "l2-cache#1"

in this case a newly allocated name is generated by `safe_name`. However
in this case it is never deallocated.

The bug was found using kmemleak reported as:

unreferenced object 0xdf532e60 (size 32):
  comm "swapper", pid 1, jiffies 4294892300 (age 1993.532s)
  hex dump (first 32 bytes):
    6c 32 2d 63 61 63 68 65 23 31 00 dd e4 dd 1e c2  l2-cache#1......
    ec d4 ba ce 04 ec cc de 8e 85 e9 ca c4 ec cc 9e  ................
  backtrace:
    [<c02d3350>] kvasprintf+0x64/0xc8
    [<c02d3400>] kasprintf+0x4c/0x5c
    [<c0453814>] safe_name.isra.1+0x80/0xc4
    [<c04545d8>] __of_attach_node_sysfs+0x6c/0x11c
    [<c075f21c>] of_core_init+0x8c/0xf8
    [<c0729594>] kernel_init_freeable+0xd4/0x208
    [<c00047e8>] kernel_init+0x24/0x11c
    [<c00158ec>] ret_from_kernel_thread+0x5c/0x64

Link: https://bugzilla.kernel.org/show_bug.cgi?id=120331

Signed-off-by: Frank Rowand <[email-masked]>
Reported-by: [email-masked]
---

changes from v1
  Move the prototype of __of_sysfs_remove_bin_file() into of_private.h

changes from v2
  Add the kfree that was in Mathieu's original patch

 drivers/of/base.c       |   30 +++++++++++++++++++++---------
 drivers/of/dynamic.c    |    2 +-
 drivers/of/of_private.h |    3 +++
 3 files changed, 25 insertions(+), 10 deletions(-)

Index: b/drivers/of/base.c
===================================================================
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -112,6 +112,7 @@ static ssize_t of_node_property_read(str
 	return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length);
 }
 
+/* always return newly allocated name, caller must free after use */
 static const char *safe_name(struct kobject *kobj, const char *orig_name)
 {
 	const char *name = orig_name;
@@ -126,9 +127,12 @@ static const char *safe_name(struct kobj
 		name = kasprintf(GFP_KERNEL, "%s#%i", orig_name, ++i);
 	}
 
-	if (name != orig_name)
+	if (name == orig_name) {
+		name = kstrdup(orig_name, GFP_KERNEL);
+	} else {
 		pr_warn("device-tree: Duplicate name in %s, renamed to \"%s\"\n",
 			kobject_name(kobj), name);
+	}
 	return name;
 }
 
@@ -159,6 +163,7 @@ int __of_add_property_sysfs(struct devic
 int __of_attach_node_sysfs(struct device_node *np)
 {
 	const char *name;
+	struct kobject *parent;
 	struct property *pp;
 	int rc;
 
@@ -171,15 +176,16 @@ int __of_attach_node_sysfs(struct device
 	np->kobj.kset = of_kset;
 	if (!np->parent) {
 		/* Nodes without parents are new top level trees */
-		rc = kobject_add(&np->kobj, NULL, "%s",
-				 safe_name(&of_kset->kobj, "base"));
+		name = safe_name(&of_kset->kobj, "base");
+		parent = NULL;
 	} else {
 		name = safe_name(&np->parent->kobj, kbasename(np->full_name));
-		if (!name || !name[0])
-			return -EINVAL;
-
-		rc = kobject_add(&np->kobj, &np->parent->kobj, "%s", name);
+		parent = &np->parent->kobj;
 	}
+	if (!name)
+		return -ENOMEM;
+	rc = kobject_add(&np->kobj, parent, "%s", name);
+	kfree(name);
 	if (rc)
 		return rc;
 
@@ -1815,6 +1821,12 @@ int __of_remove_property(struct device_n
 	return 0;
 }
 
+void __of_sysfs_remove_bin_file(struct device_node *np, struct property *prop)
+{
+	sysfs_remove_bin_file(&np->kobj, &prop->attr);
+	kfree(prop->attr.attr.name);
+}
+
 void __of_remove_property_sysfs(struct device_node *np, struct property *prop)
 {
 	if (!IS_ENABLED(CONFIG_SYSFS))
@@ -1822,7 +1834,7 @@ void __of_remove_property_sysfs(struct d
 
 	/* at early boot, bail here and defer setup to of_init() */
 	if (of_kset && of_node_is_attached(np))
-		sysfs_remove_bin_file(&np->kobj, &prop->attr);
+		__of_sysfs_remove_bin_file(np, prop);
 }
 
 /**
@@ -1895,7 +1907,7 @@ void __of_update_property_sysfs(struct d
 		return;
 
 	if (oldprop)
-		sysfs_remove_bin_file(&np->kobj, &oldprop->attr);
+		__of_sysfs_remove_bin_file(np, oldprop);
 	__of_add_property_sysfs(np, newprop);
 }
 
Index: b/drivers/of/dynamic.c
===================================================================
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -55,7 +55,7 @@ void __of_detach_node_sysfs(struct devic
 	/* only remove properties if on sysfs */
 	if (of_node_is_attached(np)) {
 		for_each_property_of_node(np, pp)
-			sysfs_remove_bin_file(&np->kobj, &pp->attr);
+			__of_sysfs_remove_bin_file(np, pp);
 		kobject_del(&np->kobj);
 	}
 
Index: b/drivers/of/of_private.h
===================================================================
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -83,6 +83,9 @@ extern int __of_attach_node_sysfs(struct
 extern void __of_detach_node(struct device_node *np);
 extern void __of_detach_node_sysfs(struct device_node *np);
 
+extern void __of_sysfs_remove_bin_file(struct device_node *np,
+				       struct property *prop);
+
 /* iterators for transactions, used for overlays */
 /* forward iterator */
 #define for_each_transaction_entry(_oft, _te) \