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From: Mathieu Malaterre <mathieu.malaterre@gmail.com>
Date: Thu, 16 Jun 2016 09:15:07 +0200
Message-ID: <CA+7wUszph+weTn=bu24d6YdkChOk39ae_dOkQXJQxykkQH0PNg@mail.gmail.com>
Subject: Re: [PATCH v2] of: fix memory leak related to safe_name()
To: Frank Rowand <frowand.list@gmail.com>
Cc: Rob Herring <robh+dt@kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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I only tested v2. I confirm this solve the symptoms I was seeing in
the bug report.

Tested-by: Mathieu Malaterre <mathieu.malaterre@gmail.com>

thanks, your patch is actually much cleaner!

On Wed, Jun 15, 2016 at 10:42 PM, Frank Rowand <frowand.list@gmail.com> wrote:
> From: Frank Rowand <frank.rowand@am.sony.com>
>
> 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 <frank.rowand@am.sony.com>
> Reported-by: mathieu.malaterre@gmail.com
> ---
>
> 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
> ===================================================================
> --- 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 +176,15 @@ 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
> ===================================================================
> --- 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) \



-- 
Mathieu