On Thu, May 20, 2021 at 3:58 AM Christian Brauner
<christian.brauner@xxxxxxxxxx> wrote:
> On Wed, May 19, 2021 at 04:00:21PM -0400, Richard Guy Briggs wrote:
> > The openat2(2) syscall was added in kernel v5.6 with commit fddb5d430ad9
> > ("open: introduce openat2(2) syscall")
> >
> > Add the openat2(2) syscall to the audit syscall classifier.
> >
> > Link: https://github.com/linux-audit/audit-kernel/issues/67
> > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> > Link: https://lore.kernel.org/r/f5f1a4d8699613f8c02ce762807228c841c2e26f.1621363275.git.rgb@xxxxxxxxxx
> > ---
> > arch/alpha/kernel/audit.c | 2 ++
> > arch/ia64/kernel/audit.c | 2 ++
> > arch/parisc/kernel/audit.c | 2 ++
> > arch/parisc/kernel/compat_audit.c | 2 ++
> > arch/powerpc/kernel/audit.c | 2 ++
> > arch/powerpc/kernel/compat_audit.c | 2 ++
> > arch/s390/kernel/audit.c | 2 ++
> > arch/s390/kernel/compat_audit.c | 2 ++
> > arch/sparc/kernel/audit.c | 2 ++
> > arch/sparc/kernel/compat_audit.c | 2 ++
> > arch/x86/ia32/audit.c | 2 ++
> > arch/x86/kernel/audit_64.c | 2 ++
> > include/linux/auditsc_classmacros.h | 1 +
> > kernel/auditsc.c | 3 +++
> > lib/audit.c | 4 ++++
> > lib/compat_audit.c | 4 ++++
> > 16 files changed, 36 insertions(+)
...
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index d775ea16505b..3f59ab209dfd 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -76,6 +76,7 @@
> > #include <linux/fsnotify_backend.h>
> > #include <uapi/linux/limits.h>
> > #include <uapi/linux/netfilter/nf_tables.h>
> > +#include <uapi/linux/openat2.h>
> >
> > #include "audit.h"
> >
> > @@ -196,6 +197,8 @@ static int audit_match_perm(struct audit_context *ctx, int mask)
> > return ((mask & AUDIT_PERM_WRITE) && ctx->argv[0] == SYS_BIND);
> > case AUDITSC_EXECVE:
> > return mask & AUDIT_PERM_EXEC;
> > + case AUDITSC_OPENAT2:
> > + return mask & ACC_MODE((u32)((struct open_how *)ctx->argv[2])->flags);
>
> That's a lot of dereferncing, casting and masking all at once. Maybe a
> small static inline helper would be good for the sake of legibility? Sm
> like:
>
> static inline u32 audit_openat2_acc(struct open_how *how, int mask)
> {
> u32 flags = how->flags;
> return mask & ACC_MODE(flags);
> }
>
> but not sure. Just seems more legible to me.
> Otherwise.
I'm on the fence about this. I understand Christian's concern, but I
have a bit of hatred towards single caller functions like this. Since
this function isn't really high-touch, and I don't expect that to
change in the near future, let's leave the casting mess as-is.
--
paul moore
www.paul-moore.com
