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Subject[RFC][PATCH 03/10] Task watchers v2 Register audit task watcher
Change audit to register a task watcher function rather than modify
the copy_process() and do_exit() paths directly.

Removes an unlikely() hint from kernel/exit.c:
if (unlikely(tsk->audit_context))
audit_free(tsk);
This use of unlikely() is an artifact of audit_free()'s former invocation from
__put_task_struct() (commit: fa84cb935d4ec601528f5e2f0d5d31e7876a5044).
Clearly in the __put_task_struct() path it would be called much more frequently
than do_exit() and hence the use of unlikely() there was justified. However, in
the new location the hint most likely offers no measurable performance impact.
Signed-off-by: Matt Helsley <matthltc@us.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Steve Grubb <sgrubb@redhat.com>
Cc: linux-audit@redhat.com
---
include/linux/audit.h | 4 ----
kernel/auditsc.c | 10 +++++++---
kernel/exit.c | 3 ---
kernel/fork.c | 7 +------
4 files changed, 8 insertions(+), 16 deletions(-)
Index: linux-2.6.18-mm1/kernel/auditsc.c
===================================================================
--- linux-2.6.18-mm1.orig/kernel/auditsc.c
+++ linux-2.6.18-mm1/kernel/auditsc.c
@@ -63,10 +63,11 @@
#include <linux/list.h>
#include <linux/tty.h>
#include <linux/selinux.h>
#include <linux/binfmts.h>
#include <linux/syscalls.h>
+#include <linux/task_watchers.h>

#include "audit.h"

extern struct list_head audit_filter_list[];

@@ -674,11 +675,11 @@ static inline struct audit_context *audi
* Filter on the task information and allocate a per-task audit context
* if necessary. Doing so turns on system call auditing for the
* specified task. This is called from copy_process, so no lock is
* needed.
*/
-int audit_alloc(struct task_struct *tsk)
+static int audit_alloc(unsigned long val, struct task_struct *tsk)
{
struct audit_context *context;
enum audit_state state;

if (likely(!audit_enabled))
@@ -700,10 +701,11 @@ int audit_alloc(struct task_struct *tsk)

tsk->audit_context = context;
set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
return 0;
}
+task_watcher_func(init, audit_alloc);

static inline void audit_free_context(struct audit_context *context)
{
struct audit_context *previous;
int count = 0;
@@ -1029,28 +1031,30 @@ static void audit_log_exit(struct audit_
* audit_free - free a per-task audit context
* @tsk: task whose audit context block to free
*
* Called from copy_process and do_exit
*/
-void audit_free(struct task_struct *tsk)
+static int audit_free(unsigned long val, struct task_struct *tsk)
{
struct audit_context *context;

context = audit_get_context(tsk, 0, 0);
if (likely(!context))
- return;
+ return 0;

/* Check for system calls that do not go through the exit
* function (e.g., exit_group), then free context block.
* We use GFP_ATOMIC here because we might be doing this
* in the context of the idle thread */
/* that can happen only if we are called from do_exit() */
if (context->in_syscall && context->auditable)
audit_log_exit(context, tsk);

audit_free_context(context);
+ return 0;
}
+task_watcher_func(free, audit_free);

/**
* audit_syscall_entry - fill in an audit record at syscall entry
* @tsk: task being audited
* @arch: architecture type
Index: linux-2.6.18-mm1/include/linux/audit.h
===================================================================
--- linux-2.6.18-mm1.orig/include/linux/audit.h
+++ linux-2.6.18-mm1/include/linux/audit.h
@@ -326,12 +326,10 @@ struct mqstat;
extern int __init audit_register_class(int class, unsigned *list);
extern int audit_classify_syscall(int abi, unsigned syscall);
#ifdef CONFIG_AUDITSYSCALL
/* These are defined in auditsc.c */
/* Public API */
-extern int audit_alloc(struct task_struct *task);
-extern void audit_free(struct task_struct *task);
extern void audit_syscall_entry(int arch,
int major, unsigned long a0, unsigned long a1,
unsigned long a2, unsigned long a3);
extern void audit_syscall_exit(int failed, long return_code);
extern void __audit_getname(const char *name);
@@ -426,12 +424,10 @@ static inline int audit_mq_getsetattr(mq
return __audit_mq_getsetattr(mqdes, mqstat);
return 0;
}
extern int audit_n_rules;
#else
-#define audit_alloc(t) ({ 0; })
-#define audit_free(t) do { ; } while (0)
#define audit_syscall_entry(ta,a,b,c,d,e) do { ; } while (0)
#define audit_syscall_exit(f,r) do { ; } while (0)
#define audit_dummy_context() 1
#define audit_getname(n) do { ; } while (0)
#define audit_putname(n) do { ; } while (0)
Index: linux-2.6.18-mm1/kernel/fork.c
===================================================================
--- linux-2.6.18-mm1.orig/kernel/fork.c
+++ linux-2.6.18-mm1/kernel/fork.c
@@ -37,11 +37,10 @@
#include <linux/jiffies.h>
#include <linux/futex.h>
#include <linux/rcupdate.h>
#include <linux/ptrace.h>
#include <linux/mount.h>
-#include <linux/audit.h>
#include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
@@ -1103,15 +1102,13 @@ static struct task_struct *copy_process(
p->blocked_on = NULL; /* not blocked yet */
#endif

if ((retval = security_task_alloc(p)))
goto bad_fork_cleanup_policy;
- if ((retval = audit_alloc(p)))
- goto bad_fork_cleanup_security;
/* copy all the process information */
if ((retval = copy_semundo(clone_flags, p)))
- goto bad_fork_cleanup_audit;
+ goto bad_fork_cleanup_security;
if ((retval = copy_files(clone_flags, p)))
goto bad_fork_cleanup_semundo;
if ((retval = copy_fs(clone_flags, p)))
goto bad_fork_cleanup_files;
if ((retval = copy_sighand(clone_flags, p)))
@@ -1282,12 +1279,10 @@ bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
exit_files(p); /* blocking */
bad_fork_cleanup_semundo:
exit_sem(p);
-bad_fork_cleanup_audit:
- audit_free(p);
bad_fork_cleanup_security:
security_task_free(p);
bad_fork_cleanup_policy:
#ifdef CONFIG_NUMA
mpol_free(p->mempolicy);
Index: linux-2.6.18-mm1/kernel/exit.c
===================================================================
--- linux-2.6.18-mm1.orig/kernel/exit.c
+++ linux-2.6.18-mm1/kernel/exit.c
@@ -36,11 +36,10 @@
#include <linux/cn_proc.h>
#include <linux/mutex.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/pipe_fs_i.h>
-#include <linux/audit.h> /* for audit_free() */
#include <linux/resource.h>
#include <linux/blkdev.h>
#include <linux/task_watchers.h>

#include <asm/uaccess.h>
@@ -908,12 +907,10 @@ fastcall NORET_TYPE void do_exit(long co
exit_robust_list(tsk);
#if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
if (unlikely(tsk->compat_robust_list))
compat_exit_robust_list(tsk);
#endif
- if (unlikely(tsk->audit_context))
- audit_free(tsk);
taskstats_exit_send(tsk, tidstats, group_dead, mycpu);
taskstats_exit_free(tidstats);

exit_mm(tsk);
notify_task_watchers(WATCH_TASK_FREE, code, tsk);
--
-
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