[ghak90,V9,07/13] audit: add support for non-syscall auxiliary records
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Message ID 21e6c4e1ac179c8dcf35803e603899ccfc69300a.1593198710.git.rgb@redhat.com
State New
Headers show
Series
  • audit: implement container identifier
Related show

Commit Message

Richard Guy Briggs June 27, 2020, 1:20 p.m. UTC
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>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
---
 include/linux/audit.h |  8 ++++++++
 kernel/audit.h        |  1 +
 kernel/auditsc.c      | 33 ++++++++++++++++++++++++++++-----
 3 files changed, 37 insertions(+), 5 deletions(-)

Comments

Paul Moore July 5, 2020, 3:11 p.m. UTC | #1
On Sat, Jun 27, 2020 at 9:22 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.

We've had some good discussions on the list about why we can't reuse
the "in_syscall" field and need to add a "local" field, I think it
would be good to address that here in the commit description.

> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> Acked-by: Serge Hallyn <serge@hallyn.com>
> Acked-by: Neil Horman <nhorman@tuxdriver.com>
> Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> ---
>  include/linux/audit.h |  8 ++++++++
>  kernel/audit.h        |  1 +
>  kernel/auditsc.c      | 33 ++++++++++++++++++++++++++++-----
>  3 files changed, 37 insertions(+), 5 deletions(-)

...

> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 9e79645e5c0e..935eb3d2cde9 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -908,11 +908,13 @@ 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() */

At this point I think it's clear we need a respin so I'm not going to
preface all of my nitpick comments as such, although this definitely
would qualify ...

I don't believe audit_tg() doesn't exist yet, likely coming later in
this patchset, so please remove this comment as it doesn't make sense
in this context.

To be frank, don't re-add the comment later in the patchset either.
Comments like these tend to be fragile and don't really add any great
insight.  The audit_tg() function can, and most likely will, be
modified at some point in the future such that the comment above no
longer applies, and there is a reasonable chance that when it does the
above comment will not be updated.  Further, anyone modifying the
audit_alloc_context() is going to look at the callers (rather they
*should* look at the callers) and will notice the no-sleep
requirements.

> @@ -960,8 +963,27 @@ 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;
> +
> +       context = audit_alloc_context(AUDIT_RECORD_CONTEXT, gfpflags);
> +       if (!context) {
> +               audit_log_lost("out of memory in audit_alloc_local");
> +               goto out;

You might as well just return NULL here, no need to jump and then return NULL.


> +       }
> +       context->serial = audit_serial();
> +       ktime_get_coarse_real_ts64(&context->ctime);
> +       context->local = true;
> +out:
> +       return context;
> +}
> +EXPORT_SYMBOL(audit_alloc_local);

--
paul moore
www.paul-moore.com

Patch
diff mbox series

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 89cf7c66abe6..15d0defc5193 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -330,6 +330,8 @@  static inline int audit_signal_info(int sig, struct task_struct *t)
 
 /* 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);
@@ -592,6 +594,12 @@  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 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 0c9446f8d52c..a7f88d76163f 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -98,6 +98,7 @@  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 9e79645e5c0e..935eb3d2cde9 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -908,11 +908,13 @@  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;
@@ -948,7 +950,8 @@  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;
@@ -960,8 +963,27 @@  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;
+
+	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);
@@ -972,6 +994,7 @@  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,
@@ -2204,7 +2227,7 @@  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();