[RFC PATCH v1 02/11] security: Add LSM_AUDIT_DATA_NS for namespace audit records

[Mickaël Salaün]

On Wed, Apr 01, 2026 at 06:38:34PM +0200, Mickaël Salaün wrote:
> On Wed, Mar 25, 2026 at 01:32:42PM +0100, Christian Brauner wrote:
> > On Thu, Mar 12, 2026 at 11:04:35AM +0100, Mickaël Salaün wrote:
> > > Add a new LSM audit data type LSM_AUDIT_DATA_NS that logs namespace
> > > information in audit records.  Two fields are provided, matching the
> > > field names of struct ns_common:
> > > 
> > > - ns_type: the CLONE_NEW* flag identifying the namespace type, logged in
> > >   hexadecimal.
> > > 
> > > - inum: the proc inode number identifying a specific namespace instance.
> > >   Namespace inode numbers are allocated by proc_alloc_inum() via
> > >   ida_alloc_max() bounded to UINT_MAX, so the value always fits in 32
> > >   bits.
> > > 
> > > A new audit data type is needed because no existing LSM_AUDIT_DATA_*
> > > type carries namespace information.  The closest alternatives (e.g.
> > > LSM_AUDIT_DATA_TASK or LSM_AUDIT_DATA_NONE with custom strings) would
> > > either lose the namespace type or require ad-hoc formatting that
> > > bypasses the structured audit data union.
> > > 
> > > Cc: Christian Brauner <brauner at kernel.org>
> > > Cc: Günther Noack <gnoack at google.com>
> > > Cc: Paul Moore <paul at paul-moore.com>
> > > Signed-off-by: Mickaël Salaün <mic at digikod.net>
> > > ---
> > >  include/linux/lsm_audit.h | 5 +++++
> > >  security/lsm_audit.c      | 4 ++++
> > >  2 files changed, 9 insertions(+)
> > > 
> > > diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
> > > index 382c56a97bba..6e20a56b8c22 100644
> > > --- a/include/linux/lsm_audit.h
> > > +++ b/include/linux/lsm_audit.h
> > > @@ -78,6 +78,7 @@ struct common_audit_data {
> > >  #define LSM_AUDIT_DATA_NOTIFICATION 16
> > >  #define LSM_AUDIT_DATA_ANONINODE	17
> > >  #define LSM_AUDIT_DATA_NLMSGTYPE	18
> > > +#define LSM_AUDIT_DATA_NS		19
> > >  	union 	{
> > >  		struct path path;
> > >  		struct dentry *dentry;
> > > @@ -100,6 +101,10 @@ struct common_audit_data {
> > >  		int reason;
> > >  		const char *anonclass;
> > >  		u16 nlmsg_type;
> > > +		struct {
> > > +			u32 ns_type;
> > > +			unsigned int inum;
> > 
> > fwiw, you might want to start the 64-bit namespace id as well.
> > But either way:
> 
> Right now these numbers are generated by ida_alloc_max(), which return
> an int.  Is there an ongoing patch series for this change?

OK, we should not use the inode's number (32-bit) but the namespace ID
(64-bit) which is readable with the NS_GET_ID IOCTL on the namespace
FDs.  I'll use that with ns_id instead of inum.  I'll also update the
Landlock code and tests accordingly.