of: fix memory leak related to safe_name()

From: Frank Rowand <[email protected]>

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 protected]>

Reported-by [email protected]

---

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

 drivers/of/base.c       |   29 ++++++++++++++++++++---------
 drivers/of/dynamic.c    |    2 +-
 drivers/of/of_private.h |    3 +++
 3 files changed, 24 insertions(+), 10 deletions(-)

Index: b/drivers/of/base.c
===================================================================

drivers/of/base.c +20 -9

@@ -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 +176,15 @@ 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);
        if (rc)
                return rc;
 

@@ -1815,6 +1820,12 @@ 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 +1833,7 @@ 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 +1906,7 @@ 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
===================================================================

drivers/of/dynamic.c +1 -1

@@ -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
===================================================================

drivers/of/of_private.h +3 -0

@@ -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) \

I only tested v2. I confirm this solve the symptoms I was seeing in the bug report.

Tested-by Mathieu Malaterre <[email protected]>

thanks, your patch is actually much cleaner!

Quoted 150 lines · Frank Rowand

From: Frank Rowand <[email protected]>

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 protected]>

Reported-by [email protected]

---

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

 drivers/of/base.c       |   29 ++++++++++++++++++++---------
 drivers/of/dynamic.c    |    2 +-
 drivers/of/of_private.h |    3 +++
 3 files changed, 24 insertions(+), 10 deletions(-)

Index: b/drivers/of/base.c
===================================================================

drivers/of/base.c +20 -9

@@ -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 +176,15 @@ 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);
        if (rc)
                return rc;
 

@@ -1815,6 +1820,12 @@ 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 +1833,7 @@ 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 +1906,7 @@ 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
===================================================================

drivers/of/dynamic.c +1 -1

@@ -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
===================================================================

drivers/of/of_private.h extern int __of_attach_node_sysfs(struct · line 91

Quoted 9 lines

drivers/of/of_private.h +3 -0

@@ -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) \

--
Mathieu

Sorry, symptoms not solved. According to kmemleak, I have now:

[  661.323100] kmemleak: 100 new suspected memory leaks (see
/sys/kernel/debug/kmemleak)
[ 1260.226120] kmemleak: 1 new suspected memory leaks (see

/sys/kernel/debug/kmemleak)

# head -40 /sys/kernel/debug/kmemleak
unreferenced object 0xdf5326a0 (size 32):
  comm "swapper", pid 1, jiffies 4294892300 (age 2564.708s)
  hex dump (first 32 bytes):
    62 61 73 65 00 00 4c d8 c5 78 df dc cc 43 e4 bc  base..L..x...C..
    c4 c8 ec 8c ee de ce cf e8 c9 8a ea dc cc c6 fd  ................
  backtrace:
    [<c014d4d8>] kstrdup+0x48/0x88
    [<c0454678>] __of_attach_node_sysfs+0xf0/0x100
    [<c075f21c>] of_core_init+0x8c/0xf8
    [<c0729594>] kernel_init_freeable+0xd4/0x208
    [<c00047e8>] kernel_init+0x24/0x11c
    [<c00158ec>] ret_from_kernel_thread+0x5c/0x64