Re: [PATCH ghak90 (was ghak32) V4 05/10] audit: add support for non-syscall auxiliary records

Paul Moore
2018-10-19T23:17:18Z

On Sun, Aug 5, 2018 at 4:33 AM Richard Guy Briggs <rgb@redhat.com> 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@redhat.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> ---
> include/linux/audit.h | 8 ++++++++
> kernel/audit.h | 1 +
> kernel/auditsc.c | 33 ++++++++++++++++++++++++++++-----
> 3 files changed, 37 insertions(+), 5 deletions(-)

I'm not in love with the local flag, and the whole local context in
general, but that's a larger discussion and not something I want to
force on this patchset; we can fix it later.

I think this patch looks fine, but it seems a bit odd standalone; it's
almost always better to include new capabilities/functions in the same
patch as the user. Since the only user is the networking bits, it
might make more sense to fold this patch into that one.

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 4f514ed..1f340ad 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -234,7 +234,9 @@ struct audit_task_info {
> extern struct audit_task_info init_struct_audit;
> extern void __init audit_task_init(void);
> extern int audit_alloc(struct task_struct *task);
> +extern struct audit_context *audit_alloc_local(gfp_t gfpflags);
> extern void audit_free(struct task_struct *task);
> +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);
> @@ -495,6 +497,12 @@ static inline int audit_alloc(struct task_struct *task)
> {
> return 0;
> }
> +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_free(struct task_struct *task)
> { }
> static inline void audit_syscall_entry(int major, unsigned long a0,
> diff --git a/kernel/audit.h b/kernel/audit.h
> index 1cf1c35..a6d00a5 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -110,6 +110,7 @@ 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 cdb24cf..7627f21 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -913,11 +913,13 @@ 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;
> @@ -970,7 +972,8 @@ int audit_alloc(struct task_struct *tsk)
> return 0;
> }
>
> - if (!(context = audit_alloc_context(state))) {
> + context = audit_alloc_context(state, GFP_KERNEL);
> + if (!(context)) {
> tsk->audit = NULL;
> kmem_cache_free(audit_task_cache, info);
> kfree(key);
> @@ -991,8 +994,27 @@ struct audit_task_info init_struct_audit = {
> .ctx = NULL,
> };
>
> -static inline void audit_free_context(struct audit_context *context)
> +struct audit_context *audit_alloc_local(gfp_t gfpflags)
> {
> + struct audit_context *context;
> +
> + if (!audit_ever_enabled)
> + return NULL; /* Return if not auditing. */
> +
> + context = audit_alloc_context(AUDIT_RECORD_CONTEXT, gfpflags);
> + if (!context)
> + return NULL;
> + context->serial = audit_serial();
> + context->ctime = current_kernel_time64();
> + context->local = true;
> + 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);
> @@ -1002,6 +1024,7 @@ 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,
> @@ -2024,7 +2047,7 @@ 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();

--
paul moore