[PATCH ghak90 V5 06/10] audit: add support for non-syscall auxiliary records

[Neil Horman]

On Fri, Mar 15, 2019 at 02:29:54PM -0400, Richard Guy Briggs wrote:
> Standalone audit records have the timestamp and serial number generated
> on the fly and as such are unique, making them standalone.  This new
> function audit_alloc_local() generates a local audit context that will
> be used only for a standalone record and its auxiliary record(s).  The
> context is discarded immediately after the local associated records are
> produced.
> 
> Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
> Acked-by: Serge Hallyn <serge at hallyn.com>
> ---
>  include/linux/audit.h |  8 ++++++++
>  kernel/audit.h        |  1 +
>  kernel/auditsc.c      | 35 ++++++++++++++++++++++++++++++-----
>  3 files changed, 39 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index ebd6625ca80e..6db5aba7cc01 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -285,6 +285,8 @@ static inline void audit_log_contid(struct audit_context *context, u64 contid)
>  
>  /* These are defined in auditsc.c */
>  				/* Public API */
> +extern struct audit_context *audit_alloc_local(gfp_t gfpflags);
> +extern void audit_free_context(struct audit_context *context);
>  extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
>  				  unsigned long a2, unsigned long a3);
>  extern void __audit_syscall_exit(int ret_success, long ret_value);
> @@ -512,6 +514,12 @@ static inline void audit_fanotify(unsigned int response)
>  extern int audit_n_rules;
>  extern int audit_signals;
>  #else /* CONFIG_AUDITSYSCALL */
> +static inline struct audit_context *audit_alloc_local(gfp_t gfpflags)
> +{
> +	return NULL;
> +}
> +static inline void audit_free_context(struct audit_context *context)
> +{ }
>  static inline void audit_syscall_entry(int major, unsigned long a0,
>  				       unsigned long a1, unsigned long a2,
>  				       unsigned long a3)
> diff --git a/kernel/audit.h b/kernel/audit.h
> index c5ac6436317e..2a1a8b8a8019 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -111,6 +111,7 @@ struct audit_proctitle {
>  struct audit_context {
>  	int		    dummy;	/* must be the first element */
>  	int		    in_syscall;	/* 1 if task is in a syscall */
> +	bool		    local;	/* local context needed */
>  	enum audit_state    state, current_state;
>  	unsigned int	    serial;     /* serial number for record */
>  	int		    major;      /* syscall number */
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index f04e115df5dc..aa5d13b4fbbb 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -872,11 +872,13 @@ static inline void audit_free_aux(struct audit_context *context)
>  	}
>  }
>  
> -static inline struct audit_context *audit_alloc_context(enum audit_state state)
> +static inline struct audit_context *audit_alloc_context(enum audit_state state,
> +							gfp_t gfpflags)
>  {
>  	struct audit_context *context;
>  
> -	context = kzalloc(sizeof(*context), GFP_KERNEL);
> +	/* We can be called in atomic context via audit_tg() */
> +	context = kzalloc(sizeof(*context), gfpflags);
>  	if (!context)
>  		return NULL;
>  	context->state = state;
> @@ -912,7 +914,8 @@ int audit_alloc_syscall(struct task_struct *tsk)
>  		return 0;
>  	}
>  
> -	if (!(context = audit_alloc_context(state))) {
> +	context = audit_alloc_context(state, GFP_KERNEL);
> +	if (!context) {
>  		kfree(key);
>  		audit_log_lost("out of memory in audit_alloc_syscall");
>  		return -ENOMEM;
> @@ -924,8 +927,29 @@ int audit_alloc_syscall(struct task_struct *tsk)
>  	return 0;
>  }
>  
> -static inline void audit_free_context(struct audit_context *context)
> +struct audit_context *audit_alloc_local(gfp_t gfpflags)
>  {
> +	struct audit_context *context = NULL;
> +
> +	if (!audit_ever_enabled)
> +		goto out; /* Return if not auditing. */
> +	context = audit_alloc_context(AUDIT_RECORD_CONTEXT, gfpflags);
> +	if (!context) {
> +		audit_log_lost("out of memory in audit_alloc_local");
> +		goto out;
> +	}
> +	context->serial = audit_serial();
> +	ktime_get_coarse_real_ts64(&context->ctime);
> +	context->local = true;
> +out:
> +	return context;
> +}
> +EXPORT_SYMBOL(audit_alloc_local);
> +
> +void audit_free_context(struct audit_context *context)
> +{
> +	if (!context)
> +		return;
>  	audit_free_names(context);
>  	unroll_tree_refs(context, NULL, 0);
>  	free_tree_refs(context);
> @@ -935,6 +959,7 @@ static inline void audit_free_context(struct audit_context *context)
>  	audit_proctitle_free(context);
>  	kfree(context);
>  }
> +EXPORT_SYMBOL(audit_free_context);
>  
>  static int audit_log_pid_context(struct audit_context *context, pid_t pid,
>  				 kuid_t auid, kuid_t uid, unsigned int sessionid,
> @@ -2163,7 +2188,7 @@ void __audit_inode_child(struct inode *parent,
>  int auditsc_get_stamp(struct audit_context *ctx,
>  		       struct timespec64 *t, unsigned int *serial)
>  {
> -	if (!ctx->in_syscall)
> +	if (!ctx->in_syscall && !ctx->local)
>  		return 0;
>  	if (!ctx->serial)
>  		ctx->serial = audit_serial();
> -- 
> 1.8.3.1
> 
> 
Acked-by: Neil Horman <nhorman at tuxdriver.com>