ACK: [SRU Bionic/Focal/Jammy/HWE-5.17/Kinetic/Unstable] UBUNTU: SAUCE: fs: fix UAF/GPF bug in nilfs_mdt_destroy

[Tim Gardner]

On 9/19/22 14:05, Thadeu Lima de Souza Cascardo wrote:
> From: Dongliang Mu <mudongliangabcd at gmail.com>
> 
> In alloc_inode, inode_init_always() could return -ENOMEM if
> security_inode_alloc() fails, which causes inode->i_private
> uninitialized. Then nilfs_is_metadata_file_inode() returns
> true and nilfs_free_inode() wrongly calls nilfs_mdt_destroy(),
> which frees the uninitialized inode->i_private
> and leads to crashes(e.g., UAF/GPF).
> 
> Fix this by moving security_inode_alloc just prior to
> this_cpu_inc(nr_inodes)
> 
> Link: https://lkml.kernel.org/r/CAFcO6XOcf1Jj2SeGt=jJV59wmhESeSKpfR0omdFRq+J9nD1vfQ@mail.gmail.com
> Reported-by: butt3rflyh4ck <butterflyhuangxx at gmail.com>
> Reported-by: Hao Sun <sunhao.th at gmail.com>
> Reported-by: Jiacheng Xu <stitch at zju.edu.cn>
> Reviewed-by: Christian Brauner (Microsoft) <brauner at kernel.org>
> Signed-off-by: Dongliang Mu <mudongliangabcd at gmail.com>
> Cc: Al Viro <viro at zeniv.linux.org.uk>
> Cc: stable at vger.kernel.org
> Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
> (cherry picked from commit dcd684c9aafe2ba01264c9f9d7480e16c89a3a4b linux-next.git)
> CVE-2022-2978
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> ---
>   fs/inode.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/inode.c b/fs/inode.c
> index ba1de23c13c1..4aecd93e1d55 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -192,8 +192,6 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
>   	inode->i_wb_frn_history = 0;
>   #endif
>   
> -	if (security_inode_alloc(inode))
> -		goto out;
>   	spin_lock_init(&inode->i_lock);
>   	lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
>   
> @@ -228,6 +226,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
>   	inode->i_fsnotify_mask = 0;
>   #endif
>   	inode->i_flctx = NULL;
> +
> +	if (security_inode_alloc(inode))
> +		goto out;
>   	this_cpu_inc(nr_inodes);
>   
>   	return 0;
Acked-by: Tim Gardner <tim.gardner at canonical.com>

-- 
-----------
Tim Gardner
Canonical, Inc