Re: [PATCH v2 01/13] audit: log all six syscall arguments in the SYSCALL record

[Ricardo Robaina]

On Thu, Sep 3, 2026 at 5:22 AM Will Deacon <will@xxxxxxxxxx> wrote:
>
> On Wed, Sep 02, 2026 at 11:43:34AM -0300, Ricardo Robaina wrote:
> > The SYSCALL record currently logs only four of the six syscall
> > arguments (a0-a3). The remaining two are captured but silently
> > discarded before reaching the audit context. This leads to the
> > need for auxiliary records when audit-relevant data lands in the
> > 5th or 6th argument of a syscall.
> >
> > Extend the SYSCALL record to log all six arguments, by adding
> > arguments a4 and a5 (5th and 6th syscall arguments respectively)
> > inline within the existing record. Also add the two new args to
> > the audit rules switch case, so audit rules can filter on them.
> >
> > Rather than plumbing two more register arguments through every
> > architecture's syscall entry path, change __audit_syscall_entry()
> > to take a pointer to pt_regs and use syscall_get_arguments() to
> > retrieve all six arguments.
> >
> >  audit-testsuite# make test
> >  audit-testsuite# ausearch -i -m SYSCALL
> >  ...
> >  type=SYSCALL ... syscall=sendto success=yes exit=1088 a0=0x4
> >   a1=0x7ffe43518b60 a2=0x440 a3=0x0 a4=7ffe43518b4c a5=c
> >  type=SYSCALL ... syscall=openat2 success=yes exit=4 a0=0x3
> >   a1=0x7fffc74692c8 a2=0x7fffc7467390 a3=0x18 a4=0 a5=7fffc74674f8
> >  type=SYSCALL ... syscall=openat success=yes exit=3 a0=AT_FDCWD
> >   a1=0x557ced4141a2 a2=O_RDWR|O_NONBLOCK a3=0x0 a4=0 a5=0
> >  ...
> >
> > Suggested-by: Will Deacon <will@xxxxxxxxxx>
> > Link: https://lore.kernel.org/audit/CAHC9VhSjEt_-Bsra4AEqWv+Daw5Ff=gqy7dX4Ah11RVhdyCBUQ@xxxxxxxxxxxxxx/T/#t
> > Signed-off-by: Ricardo Robaina <rrobaina@xxxxxxxxxx>
> > ---
> >  include/linux/audit.h         | 13 ++++---------
> >  include/uapi/linux/audit.h    |  2 ++
> >  kernel/audit.h                |  2 +-
> >  kernel/auditfilter.c          |  2 ++
> >  kernel/auditsc.c              | 19 ++++++++-----------
> >  kernel/entry/syscall-common.c |  4 +---
> >  6 files changed, 18 insertions(+), 24 deletions(-)
> >
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index 45abb3722d30..9ce5962bc537 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -323,8 +323,7 @@ extern int  audit_alloc(struct task_struct *task);
> >  extern void __audit_free(struct task_struct *task);
> >  extern void __audit_uring_entry(u8 op);
> >  extern void __audit_uring_exit(int success, long code);
> > -extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
> > -                               unsigned long a2, unsigned long a3);
> > +extern void __audit_syscall_entry(int major, struct pt_regs *regs);
> >  extern void __audit_syscall_exit(int ret_success, long ret_value);
> >  extern void __audit_getname(struct filename *name);
> >  extern void __audit_inode(struct filename *name, const struct dentry *dentry,
> > @@ -373,12 +372,10 @@ static inline void audit_uring_exit(int success, long code)
> >       if (unlikely(audit_context()))
> >               __audit_uring_exit(success, code);
> >  }
> > -static inline void audit_syscall_entry(int major, unsigned long a0,
> > -                                    unsigned long a1, unsigned long a2,
> > -                                    unsigned long a3)
> > +static inline void audit_syscall_entry(int major, struct pt_regs *regs)
> >  {
> >       if (unlikely(audit_context()))
> > -             __audit_syscall_entry(major, a0, a1, a2, a3);
> > +             __audit_syscall_entry(major, regs);
> >  }
>
> Won't this (temporarily) break the build? Maybe you need to introduce a
> new helper e.g. audit_syscall_entry_regs(), then convert everybody over
> to that, then rename it to audit_syscall_entry() at the end to keep the
> series bisectable.
>
> Will
>

Yes, you're right Will. Thanks for your suggestion I'll do that in the
next version.

Thanks!
-Ricardo