Re: [PATCH 1/8] apparmor: just use vfs_kern_mount to make .null

On 4/16/20 8:44 AM, Luis Chamberlain wrote:

On Tue, Apr 14, 2020 at 02:42:55PM +0200, Emanuele Giuseppe Esposito wrote:

quoted

aa_mk_null_file is using simple_pin_fs/simple_release_fs with local
variables as arguments, for what would amount to a simple
vfs_kern_mount/mntput pair if everything was inlined.  Just use
the normal filesystem API since the reference counting is not needed
here.

*Why* is refcounting not needed here?

The refcount is a local variable and is always 0 on entry and exit, so 
it is not necessary to have refcounting across function invocations, 
such as what simple_pin_fs and simple_release_fs provide.

Thank you,

Emanuele

    Luis

quoted

Signed-off-by: Emanuele Giuseppe Esposito <redacted>
---
  security/apparmor/apparmorfs.c | 12 ++++++------
  1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c
index 280741fc0f5f..828bb1eb77ea 100644
--- a/security/apparmor/apparmorfs.c
+++ b/security/apparmor/apparmorfs.c

@@ -2525,14 +2525,14 @@ struct path aa_null;
  
  static int aa_mk_null_file(struct dentry *parent)
  {
-	struct vfsmount *mount = NULL;
+	struct file_system_type *type = parent->d_sb->s_type;
+	struct vfsmount *mount;
  	struct dentry *dentry;
  	struct inode *inode;
-	int count = 0;
-	int error = simple_pin_fs(parent->d_sb->s_type, &mount, &count);
  
-	if (error)
-		return error;
+	mount = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
+	if (IS_ERR(mount))
+		return PTR_ERR(mount);
  
  	inode_lock(d_inode(parent));
  	dentry = lookup_one_len(NULL_FILE_NAME, parent, strlen(NULL_FILE_NAME));

@@ -2561,7 +2561,7 @@ static int aa_mk_null_file(struct dentry *parent)
  	dput(dentry);
  out:
  	inode_unlock(d_inode(parent));
-	simple_release_fs(&mount, &count);
+	mntput(mount);
  	return error;
  }
  

-- 
2.25.2