[PATCH v24 21/25] audit: add support for non-syscall auxiliary records

[Casey Schaufler]

On 1/26/2021 10:42 AM, Richard Guy Briggs wrote:
> On 2021-01-26 08:41, Casey Schaufler 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>
>> Signed-off-by: Casey Schaufler <casey at schaufler-ca.com>
>> Cc: linux-audit at redhat.com
>> To: Richard Guy Briggs <rgb at redhat.com>
> This has been minorly bothering me for several revisions...  Is there a
> way for the development/authorship to be accurately reflected
> if/when this patch is merged before the contid patch set?

I don't know the right way to do that because I had to pull
some of what was in the original patch out. Any way you would
like it done is fine with me.

>
>> ---
>>  include/linux/audit.h |  8 ++++++++
>>  kernel/audit.h        |  1 +
>>  kernel/auditsc.c      | 33 ++++++++++++++++++++++++++++-----
>>  3 files changed, 37 insertions(+), 5 deletions(-)
>>
>> diff --git a/include/linux/audit.h b/include/linux/audit.h
>> index 418a485af114..97cd7471e572 100644
>> --- a/include/linux/audit.h
>> +++ b/include/linux/audit.h
>> @@ -289,6 +289,8 @@ static inline int audit_signal_info(int sig, struct task_struct *t)
>>  				/* Public API */
>>  extern int  audit_alloc(struct task_struct *task);
>>  extern void __audit_free(struct task_struct *task);
>> +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);
>> @@ -552,6 +554,12 @@ static inline void audit_log_nfcfg(const char *name, u8 af,
>>  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 int audit_alloc(struct task_struct *task)
>>  {
>>  	return 0;
>> diff --git a/kernel/audit.h b/kernel/audit.h
>> index ce41886807bb..3f2285e1c6e0 100644
>> --- a/kernel/audit.h
>> +++ b/kernel/audit.h
>> @@ -99,6 +99,7 @@ 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 de2b2ecb3aea..479b3933d788 100644
>> --- a/kernel/auditsc.c
>> +++ b/kernel/auditsc.c
>> @@ -927,11 +927,13 @@ 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;
>> @@ -967,7 +969,8 @@ int audit_alloc(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");
>>  		return -ENOMEM;
>> @@ -979,8 +982,27 @@ int audit_alloc(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;
>> +
>> +	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_module(context);
>>  	audit_free_names(context);
>>  	unroll_tree_refs(context, NULL, 0);
>> @@ -991,6 +1013,7 @@ 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,
>> @@ -2214,7 +2237,7 @@ EXPORT_SYMBOL_GPL(__audit_inode_child);
>>  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();
>> -- 
>> 2.25.4
>>
> - RGB
>
> --
> Richard Guy Briggs <rgb at redhat.com>
> Sr. S/W Engineer, Kernel Security, Base Operating Systems
> Remote, Ottawa, Red Hat Canada
> IRC: rgb, SunRaycer
> Voice: +1.647.777.2635, Internal: (81) 32635
>