Re: [PATCH] fsnotify: add generic perm check for unlink/rmdir

Paul Moore
2022-05-18T01:17:24Z

On Tue, May 3, 2022 at 2:38 PM Guowei Du <duguoweisz@gmail.com> wrote:
>
> From: duguowei <duguowei@xiaomi.com>
>
> For now, there have been open/access/open_exec perms for file operation,
> so we add new perms check with unlink/rmdir syscall. if one app deletes
> any file/dir within pubic area, fsnotify can sends fsnotify_event to
> listener to deny that, even if the app have right dac/mac permissions.
>
> Signed-off-by: duguowei <duguowei@xiaomi.com>
> ---
> fs/notify/fsnotify.c | 2 +-
> include/linux/fs.h | 2 ++
> include/linux/fsnotify.h | 16 ++++++++++++++++
> include/linux/fsnotify_backend.h | 6 +++++-
> security/security.c | 12 ++++++++++--
> security/selinux/hooks.c | 4 ++++
> 6 files changed, 38 insertions(+), 4 deletions(-)

...

> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index e9e959343de9..f0780f0eb903 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1801,8 +1801,12 @@ static int may_create(struct inode *dir,
> }
>
> #define MAY_LINK 0
> +#ifndef MAY_UNLINK
> #define MAY_UNLINK 1
> +#endif
> +#ifndef MAY_RMDIR
> #define MAY_RMDIR 2
> +#endif

In the future if you run into a symbol collision here I would prefer
if you renamed the SELinux constants to something like SEL_MAY_LINK,
etc.

--
paul-moore.com