linux-kernel - Re: [PATCH] shmem: Use ramfs_kill_sb() for kill

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Message-Id: <20230607104313.2909afb61021a1431dc56a28@linux-foundation.org>
Date:   Wed, 7 Jun 2023 10:43:13 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     hughd@...gle.com, linux-kernel@...r.kernel.org,
        Roberto Sassu <roberto.sassu@...wei.com>,
        stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
        David Howells <dhowells@...hat.com>
Subject: Re: [PATCH] shmem: Use ramfs_kill_sb() for kill_sb method of
 ramfs-based tmpfs

(cc's added)

On Wed,  7 Jun 2023 18:15:23 +0200 Roberto Sassu <roberto.sassu@...weicloud.com> wrote:

> From: Roberto Sassu <roberto.sassu@...wei.com>
> 
> 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@...r.kernel.org # 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@...wei.com>
> ---
>  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