linux-kernel - Re: [PATCH v3 1/3] mm/shmem: check return value of shmem_init

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Date:   Mon, 6 Jun 2022 17:39:48 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Chen Wandun <chenwandun@...wei.com>
Cc:     hughd@...gle.com, akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, willy@...radead.org,
        david@...hat.com, wangkefeng.wang@...wei.com
Subject: Re: [PATCH v3 1/3] mm/shmem: check return value of
 shmem_init_inodecache

On Mon, Jun 06, 2022 at 11:45:28AM +0800, Chen Wandun wrote:
> It will result in null pointer access if shmem_init_inodecache fail,
> so check return value of shmem_init_inodecache
> 
> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
> ---
>  mm/shmem.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 12d45a03f7fc..7419ab219b97 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -3775,11 +3775,16 @@ static void shmem_init_inode(void *foo)
>  	inode_init_once(&info->vfs_inode);
>  }
>  
> -static void shmem_init_inodecache(void)
> +static int shmem_init_inodecache(void)
>  {
>  	shmem_inode_cachep = kmem_cache_create("shmem_inode_cache",
>  				sizeof(struct shmem_inode_info),
>  				0, SLAB_PANIC|SLAB_ACCOUNT, shmem_init_inode);

NACK, we cannot dereference a NULL pointer since SLAB_PANIC is passed
to kmem_cache_create().

> +
> +	if (!shmem_inode_cachep)
> +		return -ENOMEM;
> +
> +	return 0;
>  }
>  
>  static void shmem_destroy_inodecache(void)
> @@ -3923,7 +3928,9 @@ void __init shmem_init(void)
>  {
>  	int error;
>  
> -	shmem_init_inodecache();
> +	error = shmem_init_inodecache();
> +	if (error)
> +		goto out2;
>  
>  	error = register_filesystem(&shmem_fs_type);
>  	if (error) {
> -- 
> 2.25.1
> 
>