From c65234b283a65cfbfc94619655e820a5e55199eb Mon Sep 17 00:00:00 2001

From: Chen Zhongjin <chenzhongjin@huawei.com>

Date: Mon, 17 Oct 2022 09:42:30 +0800

Subject: [PATCH] configfs: fix possible memory leak in configfs_create_dir()

Git-commit: c65234b283a65cfbfc94619655e820a5e55199eb

Patch-mainline: v6.2-rc1

References: git-fixes

kmemleak reported memory leaks in configfs_create_dir():

unreferenced object 0xffff888009f6af00 (size 192):

  comm "modprobe", pid 3777, jiffies 4295537735 (age 233.784s)

  backtrace:

    kmem_cache_alloc (mm/slub.c:3250 mm/slub.c:3256 mm/slub.c:3263 mm/slub.c:3273)

    new_fragment (./include/linux/slab.h:600 fs/configfs/dir.c:163)

    configfs_register_subsystem (fs/configfs/dir.c:1857)

    basic_write (drivers/hwtracing/stm/p_basic.c:14) stm_p_basic

    do_one_initcall (init/main.c:1296)

    do_init_module (kernel/module/main.c:2455)

    ...

unreferenced object 0xffff888003ba7180 (size 96):

  comm "modprobe", pid 3777, jiffies 4295537735 (age 233.784s)

  backtrace:

    kmem_cache_alloc (mm/slub.c:3250 mm/slub.c:3256 mm/slub.c:3263 mm/slub.c:3273)

    configfs_new_dirent (./include/linux/slab.h:723 fs/configfs/dir.c:194)

    configfs_make_dirent (fs/configfs/dir.c:248)

    configfs_create_dir (fs/configfs/dir.c:296)

    configfs_attach_group.isra.28 (fs/configfs/dir.c:816 fs/configfs/dir.c:852)

    configfs_register_subsystem (fs/configfs/dir.c:1881)

    basic_write (drivers/hwtracing/stm/p_basic.c:14) stm_p_basic

    do_one_initcall (init/main.c:1296)

    do_init_module (kernel/module/main.c:2455)

    ...

This is because the refcount is not correct in configfs_make_dirent().

For normal stage, the refcount is changing as:

configfs_register_subsystem()

  configfs_create_dir()

    configfs_make_dirent()

      configfs_new_dirent() # set s_count = 1

      dentry->d_fsdata = configfs_get(sd); # s_count = 2

...

configfs_unregister_subsystem()

  configfs_remove_dir()

    remove_dir()

      configfs_remove_dirent() # s_count = 1

    dput() ...

      *dentry_unlink_inode()*

        configfs_d_iput() # s_count = 0, release

However, if we failed in configfs_create():

configfs_register_subsystem()

  configfs_create_dir()

    configfs_make_dirent() # s_count = 2

    ...

    configfs_create() # fail

    ->out_remove:

    configfs_remove_dirent(dentry)

      configfs_put(sd) # s_count = 1

      return PTR_ERR(inode);

There is no inode in the error path, so the configfs_d_iput() is lost

and makes sd and fragment memory leaked.

To fix this, when we failed in configfs_create(), manually call

configfs_put(sd) to keep the refcount correct.

Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem")

Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>

Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Takashi Iwai <tiwai@suse.de>

---

 fs/configfs/dir.c | 2 ++

 1 file changed, 2 insertions(+)

diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c

index d1f9d2632202..ec6519e1ca3b 100644

--- a/fs/configfs/dir.c

+++ b/fs/configfs/dir.c

@@ -316,6 +316,7 @@ static int configfs_create_dir(struct config_item *item, struct dentry *dentry,

 	return 0;

 out_remove:

+	configfs_put(dentry->d_fsdata);

 	configfs_remove_dirent(dentry);

 	return PTR_ERR(inode);

 }

@@ -382,6 +383,7 @@ int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,

 	return 0;

 out_remove:

+	configfs_put(dentry->d_fsdata);

 	configfs_remove_dirent(dentry);

 	return PTR_ERR(inode);

 }

-- 

2.35.3