[PATCH] shmem: Use ramfs_kill_sb() for kill_sb method of ramfs-based tmpfs

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

As the ramfs-based tmpfs uses ramfs_init_fs_context() for the
init_fs_context method, which allocates fc->s_fs_info, use ramfs_kill_sb()
to free it and avoid a memory leak.

Cc: stable@xxxxxxxxxxxxxxx # v5.4.x
Fixes: f32356261d44 ("vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API")
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
 fs/ramfs/inode.c      | 2 +-
 include/linux/ramfs.h | 1 +
 mm/shmem.c            | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ramfs/inode.c b/fs/ramfs/inode.c
index 5ba580c7883..fef477c7810 100644
--- a/fs/ramfs/inode.c
+++ b/fs/ramfs/inode.c
@@ -278,7 +278,7 @@ int ramfs_init_fs_context(struct fs_context *fc)
 	return 0;
 }
 
-static void ramfs_kill_sb(struct super_block *sb)
+void ramfs_kill_sb(struct super_block *sb)
 {
 	kfree(sb->s_fs_info);
 	kill_litter_super(sb);
diff --git a/include/linux/ramfs.h b/include/linux/ramfs.h
index 917528d102c..d506dc63dd4 100644
--- a/include/linux/ramfs.h
+++ b/include/linux/ramfs.h
@@ -7,6 +7,7 @@
 struct inode *ramfs_get_inode(struct super_block *sb, const struct inode *dir,
 	 umode_t mode, dev_t dev);
 extern int ramfs_init_fs_context(struct fs_context *fc);
+extern void ramfs_kill_sb(struct super_block *sb);
 
 #ifdef CONFIG_MMU
 static inline int
diff --git a/mm/shmem.c b/mm/shmem.c
index e40a08c5c6d..74abb97ea55 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -4196,7 +4196,7 @@ static struct file_system_type shmem_fs_type = {
 	.name		= "tmpfs",
 	.init_fs_context = ramfs_init_fs_context,
 	.parameters	= ramfs_fs_parameters,
-	.kill_sb	= kill_litter_super,
+	.kill_sb	= ramfs_kill_sb,
 	.fs_flags	= FS_USERNS_MOUNT,
 };
 
-- 
2.25.1