Re: [PATCH 2/2] acct: block access to kernel internal filesystems

[Amir Goldstein]

On Tue, Feb 11, 2025 at 6:17 PM Christian Brauner <brauner@xxxxxxxxxx> wrote:
>
> There's no point in allowing anything kernel internal nor procfs or
> sysfs.
>
> Reported-by: Zicheng Qu <quzicheng@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20250127091811.3183623-1-quzicheng@xxxxxxxxxx
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>

Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>

> ---
>  kernel/acct.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 48283efe8a12..6520baa13669 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -243,6 +243,20 @@ static int acct_on(struct filename *pathname)
>                 return -EACCES;
>         }
>
> +       /* Exclude kernel kernel internal filesystems. */
> +       if (file_inode(file)->i_sb->s_flags & (SB_NOUSER | SB_KERNMOUNT)) {
> +               kfree(acct);
> +               filp_close(file, NULL);
> +               return -EINVAL;
> +       }
> +
> +       /* Exclude procfs and sysfs. */
> +       if (file_inode(file)->i_sb->s_iflags & SB_I_USERNS_VISIBLE) {
> +               kfree(acct);
> +               filp_close(file, NULL);
> +               return -EINVAL;
> +       }
> +
>         if (!(file->f_mode & FMODE_CAN_WRITE)) {
>                 kfree(acct);
>                 filp_close(file, NULL);
>
> --
> 2.47.2
>
>