Re: [PATCH] fsnotify, lsm: Separate fsnotify_open_perm() and security_file_open()

[Amir Goldstein]

On Fri, Oct 11, 2024 at 11:42 PM Paul Moore <paul@xxxxxxxxxxxxxx> wrote:
>
> On Oct 11, 2024 Song Liu <song@xxxxxxxxxx> wrote:
> >
> > Currently, fsnotify_open_perm() is called from security_file_open(). This
> > is not right for CONFIG_SECURITY=n and CONFIG_FSNOTIFY=y case, as
> > security_file_open() in this combination will be a no-op and not call
> > fsnotify_open_perm(). Fix this by calling fsnotify_open_perm() directly.
> >
> > Signed-off-by: Song Liu <song@xxxxxxxxxx>
> > ---
> > PS: I didn't included a Fixes tag. This issue was probably introduced 15
> > years ago in [1]. If we want to back port this to stable, we will need
> > another version for older kernel because of [2].
> >
> > [1] c4ec54b40d33 ("fsnotify: new fsnotify hooks and events types for access decisions")
> > [2] 36e28c42187c ("fsnotify: split fsnotify_perm() into two hooks")
> > ---
> >  fs/open.c           | 4 ++++
> >  security/security.c | 9 +--------
> >  2 files changed, 5 insertions(+), 8 deletions(-)

Nice cleanup, but please finish off the coupling of lsm/fsnotify altogether.
I would either change the title to "decouple fsnotify from lsm" or
submit an additional patch with that title.

diff --git a/fs/notify/fanotify/Kconfig b/fs/notify/fanotify/Kconfig
index a511f9d8677b..0e36aaf379b7 100644
--- a/fs/notify/fanotify/Kconfig
+++ b/fs/notify/fanotify/Kconfig
@@ -15,7 +15,6 @@ config FANOTIFY
 config FANOTIFY_ACCESS_PERMISSIONS
        bool "fanotify permissions checking"
        depends on FANOTIFY
-       depends on SECURITY
        default n
        help
           Say Y here is you want fanotify listeners to be able to
make permissions
diff --git a/security/security.c b/security/security.c
index 6875eb4a59fc..8d238ffdeb4a 100644
--- a/security/security.c
+++ b/security/security.c
@@ -19,7 +19,6 @@
 #include <linux/kernel.h>
 #include <linux/kernel_read_file.h>
 #include <linux/lsm_hooks.h>
-#include <linux/fsnotify.h>
 #include <linux/mman.h>
 #include <linux/mount.h>
 #include <linux/personality.h>

>
> This looks fine to me, if we can get an ACK from the VFS folks I can
> merge this into the lsm/stable-6.12 tree and send it to Linus, or the
> VFS folks can do it if they prefer (my ACK is below just in case).

My preference would be to take this via the vfs or fsnotify tree.

>
> As far as stable prior to v6.8 is concerned, once this hits Linus'
> tree you can submit an adjusted backport for the older kernels to the
> stable team.

Please do NOT submit an adjustable backport.
Instead please include the following tags for the decoupling patch:

Depends-on: 36e28c42187c fsnotify: split fsnotify_perm() into two hooks
Depends-on: d9e5d31084b0 fsnotify: optionally pass access range in
file permission hooks

>
> Acked-by: Paul Moore <paul@xxxxxxxxxxxxxx>
>

Thanks,
Amir.