Re: [RFC PATCH ghak59 V1 4/6] audit: hand taken context to audit_kill_trees for syscall logging

[Paul Moore <paul@paul-moore.com>]

On Thu, Jun 14, 2018 at 4:23 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> Since the context is taken from the task in __audit_syscall_exit() and
> __audit_free(), hand it to audit_kill_trees() so it can be used to
> associate with a syscall record.  This requires adding the context
> parameter to kill_rules() rather than using the current audit_context
> (which has been taken).
>
> The callers of trim_marked() and evict_chunk() still have their context.
>
> See: https://github.com/linux-audit/audit-kernel/issues/50
> See: https://github.com/linux-audit/audit-kernel/issues/59
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> ---
>  kernel/audit.h      |  4 ++--
>  kernel/audit_tree.c | 18 ++++++++++--------
>  kernel/auditsc.c    |  4 ++--
>  3 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/audit.h b/kernel/audit.h
> index 214e149..f39f7aa 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -312,7 +312,7 @@ extern void audit_log_d_path_exe(struct audit_buffer *ab,
>  extern int audit_tag_tree(char *old, char *new);
>  extern const char *audit_tree_path(struct audit_tree *tree);
>  extern void audit_put_tree(struct audit_tree *tree);
> -extern void audit_kill_trees(struct list_head *list);
> +extern void audit_kill_trees(struct audit_context *context);
>  #else
>  #define audit_remove_tree_rule(rule) BUG()
>  #define audit_add_tree_rule(rule) -EINVAL
> @@ -321,7 +321,7 @@ extern void audit_log_d_path_exe(struct audit_buffer *ab,
>  #define audit_put_tree(tree) (void)0
>  #define audit_tag_tree(old, new) -EINVAL
>  #define audit_tree_path(rule) ""       /* never called */
> -#define audit_kill_trees(list) BUG()
> +#define audit_kill_trees(context) BUG()
>  #endif
>
>  extern char *audit_unpack_string(void **bufp, size_t *remain, size_t len);
> diff --git a/kernel/audit_tree.c b/kernel/audit_tree.c
> index a01b9da..2d3e1071 100644
> --- a/kernel/audit_tree.c
> +++ b/kernel/audit_tree.c
> @@ -493,13 +493,13 @@ static int tag_chunk(struct inode *inode, struct audit_tree *tree)
>         return 0;
>  }
>
> -static void audit_tree_log_remove_rule(struct audit_krule *rule)
> +static void audit_tree_log_remove_rule(struct audit_context *context, struct audit_krule *rule)
>  {
>         struct audit_buffer *ab;
>
>         if (!audit_enabled)
>                 return;
> -       ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_CONFIG_CHANGE);
> +       ab = audit_log_start(context, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
>         if (unlikely(!ab))
>                 return;
>         audit_log_format(ab, "op=remove_rule");
> @@ -510,7 +510,7 @@ static void audit_tree_log_remove_rule(struct audit_krule *rule)
>         audit_log_end(ab);
>  }
>
> -static void kill_rules(struct audit_tree *tree)
> +static void kill_rules(struct audit_context *context, struct audit_tree *tree)
>  {
>         struct audit_krule *rule, *next;
>         struct audit_entry *entry;
> @@ -521,7 +521,7 @@ static void kill_rules(struct audit_tree *tree)
>                 list_del_init(&rule->rlist);
>                 if (rule->tree) {
>                         /* not a half-baked one */
> -                       audit_tree_log_remove_rule(rule);
> +                       audit_tree_log_remove_rule(context, rule);
>                         if (entry->rule.exe)
>                                 audit_remove_mark(entry->rule.exe);
>                         rule->tree = NULL;
> @@ -584,7 +584,7 @@ static void trim_marked(struct audit_tree *tree)
>                 tree->goner = 1;
>                 spin_unlock(&hash_lock);
>                 mutex_lock(&audit_filter_mutex);
> -               kill_rules(tree);
> +               kill_rules(audit_context(), tree);
>                 list_del_init(&tree->list);
>                 mutex_unlock(&audit_filter_mutex);
>                 prune_one(tree);
> @@ -924,8 +924,10 @@ static void audit_schedule_prune(void)
>   * ... and that one is done if evict_chunk() decides to delay until the end
>   * of syscall.  Runs synchronously.
>   */
> -void audit_kill_trees(struct list_head *list)
> +void audit_kill_trees(struct audit_context *context)
>  {
> +       struct list_head *list = &context->killed_trees;
> +
>         audit_ctl_lock();
>         mutex_lock(&audit_filter_mutex);
>
> @@ -933,7 +935,7 @@ void audit_kill_trees(struct list_head *list)
>                 struct audit_tree *victim;
>
>                 victim = list_entry(list->next, struct audit_tree, list);
> -               kill_rules(victim);
> +               kill_rules(context, victim);
>                 list_del_init(&victim->list);
>
>                 mutex_unlock(&audit_filter_mutex);
> @@ -972,7 +974,7 @@ static void evict_chunk(struct audit_chunk *chunk)
>                 list_del_init(&owner->same_root);
>                 spin_unlock(&hash_lock);
>                 if (!postponed) {
> -                       kill_rules(owner);
> +                       kill_rules(audit_context(), owner);
>                         list_move(&owner->list, &prune_list);
>                         need_prune = 1;
>                 } else {
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index ceb1c45..2590c9e 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -1490,7 +1490,7 @@ void __audit_free(struct task_struct *tsk)
>         if (context->in_syscall && context->current_state == AUDIT_RECORD_CONTEXT)
>                 audit_log_exit(context, tsk);
>         if (!list_empty(&context->killed_trees))
> -               audit_kill_trees(&context->killed_trees);
> +               audit_kill_trees(context);

See my comment below about the ordering of audit_kill_trees() and
audit_log_exit().

>         audit_free_context(context);
>  }
> @@ -1577,7 +1577,7 @@ void __audit_syscall_exit(int success, long return_code)
>         context->prio = context->state == AUDIT_RECORD_CONTEXT ? ~0ULL : 0;
>
>         if (!list_empty(&context->killed_trees))
> -               audit_kill_trees(&context->killed_trees);
> +               audit_kill_trees(context);

I wonder if we should move the kill_trees if-block above the
audit_log_exit() block so that any records that are emitted will be
before the SYSCALL record.  I didn't chase down all the code paths,
but it seems like it should be safe, no?

>         audit_free_names(context);
>         unroll_tree_refs(context, NULL, 0);
> --
> 1.8.3.1

-- 
paul moore
www.paul-moore.com