[PATCH 6.12.y] fs: prepare for adding LSM blob to backing_file

[Sasha Levin <sashal@kernel.org>]

From: Amir Goldstein <amir73il@gmail.com>

[ Upstream commit 880bd496ec72a6dcb00cb70c430ef752ba242ae7 ]

In preparation to adding LSM blob to backing_file struct, factor out
helpers init_backing_file() and backing_file_free().

Cc: stable@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-unionfs@vger.kernel.org
Cc: linux-erofs@lists.ozlabs.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
[PM: use the term "LSM blob", fix comment style to match file]
Signed-off-by: Paul Moore <paul@paul-moore.com>
[ Used kfree() instead of kmem_cache_free(bfilp_cachep, ff) ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/file_table.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/fs/file_table.c b/fs/file_table.c
index cf3422edf737c..f7661a7087464 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -60,6 +60,12 @@ struct path *backing_file_user_path(struct file *f)
 }
 EXPORT_SYMBOL_GPL(backing_file_user_path);
 
+static inline void backing_file_free(struct backing_file *ff)
+{
+	path_put(&ff->user_path);
+	kfree(ff);
+}
+
 static inline void file_free(struct file *f)
 {
 	security_file_free(f);
@@ -67,8 +73,7 @@ static inline void file_free(struct file *f)
 		percpu_counter_dec(&nr_files);
 	put_cred(f->f_cred);
 	if (unlikely(f->f_mode & FMODE_BACKING)) {
-		path_put(backing_file_user_path(f));
-		kfree(backing_file(f));
+		backing_file_free(backing_file(f));
 	} else {
 		kmem_cache_free(filp_cachep, f);
 	}
@@ -255,6 +260,12 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
 	return f;
 }
 
+static int init_backing_file(struct backing_file *ff)
+{
+	memset(&ff->user_path, 0, sizeof(ff->user_path));
+	return 0;
+}
+
 /*
  * Variant of alloc_empty_file() that allocates a backing_file container
  * and doesn't check and modify nr_files.
@@ -277,7 +288,14 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
 		return ERR_PTR(error);
 	}
 
+	/* The f_mode flags must be set before fput(). */
 	ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT;
+	error = init_backing_file(ff);
+	if (unlikely(error)) {
+		fput(&ff->file);
+		return ERR_PTR(error);
+	}
+
 	return &ff->file;
 }
 
-- 
2.53.0