Re: Add pacct_struct to fix some pacct bugs.

[KaiGai Kohei <kaigai@ak.jp.nec.com>]

    [PACCT] avoidance to refer the last thread as a representation of the process

    When pacct facility generate an 'ac_flag' field in accounting record,
    it refers a task_struct of the thread which died last in the process.
    But any other task_structs are ignored.

    Therefore, pacct facility drops ASU flag even if root-privilege
    operations are used by any other threads except the last one.
    In addition, AFORK flag is always set when the thread of group-leader
    didn't die last, although this process has called execve() after fork().

    We have a same matter in ac_exitcode. The recorded ac_exitcode is
    an exit code of the last thread in the process. There is a possibility
    this exitcode is not the group leader's one.

    ---- in kernel/acct.c : do_acct_process() ----
            ac.ac_flag = 0;
            if (current->flags & PF_FORKNOEXEC)
                    ac.ac_flag |= AFORK;
            if (current->flags & PF_SUPERPRIV)
                    ac.ac_flag |= ASU;
            if (current->flags & PF_DUMPCORE)
                    ac.ac_flag |= ACORE;
            if (current->flags & PF_SIGNALED)
                    ac.ac_flag |= AXSIG;
                      :
                   - snip -
                      :
            ac.ac_exitcode = exitcode;
    ----------------------------------------------

    This patch fixes those matters.
    - The exit code of group leader is recorded as ac_exitcode.
    - ASU, ACORE, AXSIG flag are marked if any task_struct satisfy
      the conditions.
    - AFORK flag is marked if only group leader thread satisfy
      the condition.

    Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>

diff --git a/include/linux/acct.h b/include/linux/acct.h
index 6753687..879d441 100644
--- a/include/linux/acct.h
+++ b/include/linux/acct.h
@@ -122,20 +122,20 @@ struct acct_v3
 struct vfsmount;
 struct super_block;
 extern void acct_auto_close_mnt(struct vfsmount *m);
 extern void acct_auto_close(struct super_block *sb);
 extern void acct_init_pacct(struct pacct_struct *pacct);
-extern void acct_collect();
-extern void acct_process(long exitcode);
+extern void acct_collect(long exitcode, int group_dead);
+extern void acct_process(void);
 extern void acct_update_integrals(struct task_struct *tsk);
 extern void acct_clear_integrals(struct task_struct *tsk);
 #else
 #define acct_auto_close_mnt(x)	do { } while (0)
 #define acct_auto_close(x)	do { } while (0)
 #define acct_init_pacct(x)	do { } while (0)
-#define acct_collect()		do { } while (0)
-#define acct_process(x)		do { } while (0)
+#define acct_collect(x,y)	do { } while (0)
+#define acct_process()		do { } while (0)
 #define acct_update_integrals(x)		do { } while (0)
 #define acct_clear_integrals(task)	do { } while (0)
 #endif

 /*
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 918fdda..6905ac0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -357,10 +357,12 @@ struct sighand_struct {
 	struct k_sigaction	action[_NSIG];
 	spinlock_t		siglock;
 };

 struct pacct_struct {
+	int			ac_flag;
+	long			ac_exitcode;
 	unsigned long		ac_mem;
 };

 /*
  * NOTE! "signal_struct" does not have it's own
diff --git a/kernel/acct.c b/kernel/acct.c
index f1a4e12..7111fe7 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -73,11 +73,11 @@ int acct_parm[3] = {4, 2, 30};
 #define ACCT_TIMEOUT	(acct_parm[2])	/* foo second timeout between checks */

 /*
  * External references and all of the globals.
  */
-static void do_acct_process(long, struct file *);
+static void do_acct_process(struct file *);

 /*
  * This structure is used so that all the data protected by lock
  * can be placed in the same cache line as the lock.  This primes
  * the cache line to have the data after getting the lock.
@@ -194,11 +194,11 @@ static void acct_file_reopen(struct file
 		add_timer(&acct_globals.timer);
 	}
 	if (old_acct) {
 		mnt_unpin(old_acct->f_vfsmnt);
 		spin_unlock(&acct_globals.lock);
-		do_acct_process(0, old_acct);
+		do_acct_process(old_acct);
 		filp_close(old_acct, NULL);
 		spin_lock(&acct_globals.lock);
 	}
 }

@@ -417,11 +417,11 @@ static u32 encode_float(u64 value)
  */

 /*
  *  do_acct_process does all actual work. Caller holds the reference to file.
  */
-static void do_acct_process(long exitcode, struct file *file)
+static void do_acct_process(struct file *file)
 {
 	struct pacct_struct *pacct = &current->signal->pacct;
 	acct_t ac;
 	mm_segment_t fs;
 	unsigned long flim;
@@ -494,30 +494,22 @@ static void do_acct_process(long exitcod
 	read_lock(&tasklist_lock);	/* pin current->signal */
 	ac.ac_tty = current->signal->tty ?
 		old_encode_dev(tty_devnum(current->signal->tty)) : 0;
 	read_unlock(&tasklist_lock);

-	ac.ac_flag = 0;
-	if (current->flags & PF_FORKNOEXEC)
-		ac.ac_flag |= AFORK;
-	if (current->flags & PF_SUPERPRIV)
-		ac.ac_flag |= ASU;
-	if (current->flags & PF_DUMPCORE)
-		ac.ac_flag |= ACORE;
-	if (current->flags & PF_SIGNALED)
-		ac.ac_flag |= AXSIG;
 	spin_lock(&current->sighand->siglock);
+	ac.ac_flag = pacct->ac_flag;
 	ac.ac_mem = encode_comp_t(pacct->ac_mem);
+	ac.ac_exitcode = pacct->ac_exitcode;
 	spin_unlock(&current->sighand->siglock);
 	ac.ac_io = encode_comp_t(0 /* current->io_usage */);	/* %% */
 	ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
 	ac.ac_minflt = encode_comp_t(current->signal->min_flt +
 				     current->min_flt);
 	ac.ac_majflt = encode_comp_t(current->signal->maj_flt +
 				     current->maj_flt);
 	ac.ac_swaps = encode_comp_t(0);
-	ac.ac_exitcode = exitcode;

 	/*
          * Kernel segment override to datasegment and write it
          * to the accounting file.
          */
@@ -542,17 +534,19 @@ void acct_init_pacct(struct pacct_struct
 	memset(pacct, 0, sizeof(struct pacct_struct));
 }

 /**
  * acct_collect - collect accounting information into pacct_struct
+ * @exitcode: task exit code
+ * @group_dead: not 0, if this thread is the last one in the process.
  */
-void acct_collect(void)
+void acct_collect(long exitcode, int group_dead)
 {
 	struct pacct_struct *pacct = &current->signal->pacct;
 	unsigned long vsize = 0;

-	if (current->mm) {
+	if (group_dead && current->mm) {
 		struct vm_area_struct *vma;
 		down_read(&current->mm->mmap_sem);
 		vma = current->mm->mmap;
 		while (vma) {
 			vsize += vma->vm_end - vma->vm_start;
@@ -560,21 +554,33 @@ void acct_collect(void)
 		}
 		up_read(&current->mm->mmap_sem);
 	}

 	spin_lock(&current->sighand->siglock);
-	pacct->ac_mem = vsize / 1024;
+	if (group_dead)
+		pacct->ac_mem = vsize / 1024;
+	if (thread_group_leader(current)) {
+		pacct->ac_exitcode = exitcode;
+		if (current->flags & PF_FORKNOEXEC)
+			pacct->ac_flag |= AFORK;
+	}
+	if (current->flags & PF_SUPERPRIV)
+		pacct->ac_flag |= ASU;
+	if (current->flags & PF_DUMPCORE)
+		pacct->ac_flag |= ACORE;
+	if (current->flags & PF_SIGNALED)
+		pacct->ac_flag |= AXSIG;
 	spin_unlock(&current->sighand->siglock);
 }

 /**
  * acct_process - now just a wrapper around do_acct_process
  * @exitcode: task exit code
  *
  * handles process accounting for an exiting task
  */
-void acct_process(long exitcode)
+void acct_process()
 {
 	struct file *file = NULL;

 	/*
 	 * accelerate the common fastpath:
@@ -589,11 +595,11 @@ void acct_process(long exitcode)
 		return;
 	}
 	get_file(file);
 	spin_unlock(&acct_globals.lock);

-	do_acct_process(exitcode, file);
+	do_acct_process(file);
 	fput(file);
 }


 /**
diff --git a/kernel/exit.c b/kernel/exit.c
index 54bdbd9..9d395c7 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -893,12 +893,12 @@ fastcall NORET_TYPE void do_exit(long co
 	}
 	group_dead = atomic_dec_and_test(&tsk->signal->live);
 	if (group_dead) {
  		hrtimer_cancel(&tsk->signal->real_timer);
 		exit_itimers(tsk->signal);
-		acct_collect();
 	}
+	acct_collect(code, group_dead);
 	if (unlikely(tsk->robust_list))
 		exit_robust_list(tsk);
 #ifdef CONFIG_COMPAT
 	if (unlikely(tsk->compat_robust_list))
 		compat_exit_robust_list(tsk);
@@ -906,11 +906,11 @@ fastcall NORET_TYPE void do_exit(long co
 	if (unlikely(tsk->audit_context))
 		audit_free(tsk);
 	exit_mm(tsk);

 	if (group_dead)
-		acct_process(code);
+		acct_process();
 	exit_sem(tsk);
 	__exit_files(tsk);
 	__exit_fs(tsk);
 	exit_namespace(tsk);
 	exit_thread();

--
Open Source Software Promotion Center, NEC
KaiGai Kohei <kaigai@ak.jp.nec.com>
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