[PATCH] 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.

2 files changed, 26 insertions, 20 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index b35263137824..4c85fdf615da 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -75,7 +75,7 @@ int acct_parm[3] = {4, 2, 30};
 /*
  * 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
@@ -196,7 +196,7 @@ static void acct_file_reopen(struct file *file)
         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);
         }
@@ -419,7 +419,7 @@ 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;
@@ -496,17 +496,10 @@ static void do_acct_process(long exitcode, struct file *file)
                 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);
@@ -515,7 +508,6 @@ static void do_acct_process(long exitcode, struct file *file)
         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
@@ -544,13 +536,15 @@ void acct_init_pacct(struct pacct_struct *pacct)
 
 /**
  * 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;
@@ -562,7 +556,19 @@ void acct_collect(void)
         }
 
         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);
 }
 
@@ -572,7 +578,7 @@ void acct_collect(void)
  *
  * handles process accounting for an exiting task
  */
-void acct_process(long exitcode)
+void acct_process()
 {
         struct file *file = NULL;
 
@@ -591,7 +597,7 @@ void acct_process(long exitcode)
         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 819d82c2efba..e76bd02e930e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -894,8 +894,8 @@ fastcall NORET_TYPE void do_exit(long code)
         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);
 #if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
@@ -907,7 +907,7 @@ fastcall NORET_TYPE void do_exit(long code)
         exit_mm(tsk);
 
         if (group_dead)
-                acct_process(code);
+                acct_process();
         exit_sem(tsk);
         __exit_files(tsk);
         __exit_fs(tsk);