summaryrefslogtreecommitdiff
path: root/kernel/tsacct.c
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@tv-sign.ru>2006-10-28 10:38:50 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-28 11:30:54 -0700
commit05d5bcd60e8202e5c7b28cf61186043a4d612623 (patch)
tree7dccbeeb9d0b41103d70f89aae5eb6850f2f788c /kernel/tsacct.c
parentfca178c0c6e8d52a1875be36b070f30884ebfae9 (diff)
downloadlinux-sh-05d5bcd60e8202e5c7b28cf61186043a4d612623.tar.gz
[PATCH] bacct_add_tsk: fix unsafe and wrong parent/group_leader dereference
1. ts = timespec_sub(uptime, current->group_leader->start_time); It is possible that current != tsk. Probably it was supposed to be 'tsk->group_leader->start_time. But why we are reading group_leader's start_time ? This accounting is per thread, not per procees, I changed this to 'tsk->start_time. Please corect me. 2. stats->ac_ppid = (tsk->parent) ? tsk->parent->pid : 0; tsk->parent never == NULL, and it is unsafe to dereference it. Both the task and it's parent may exit after the caller unlocks tasklist_lock, the memory could be unmapped (DEBUG_SLAB). (And we should use ->real_parent->tgid in fact). Q: I don't understand the 'if (thread_group_leader(tsk))' check. Why it is needed ? Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Shailabh Nagar <nagar@watson.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Acked-by: Jay Lan <jlan@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel/tsacct.c')
-rw-r--r--kernel/tsacct.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/tsacct.c b/kernel/tsacct.c
index db443221ba5b..65a5036a3d95 100644
--- a/kernel/tsacct.c
+++ b/kernel/tsacct.c
@@ -36,7 +36,7 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
/* calculate task elapsed time in timespec */
do_posix_clock_monotonic_gettime(&uptime);
- ts = timespec_sub(uptime, current->group_leader->start_time);
+ ts = timespec_sub(uptime, tsk->start_time);
/* rebase elapsed time to usec */
ac_etime = timespec_to_ns(&ts);
do_div(ac_etime, NSEC_PER_USEC);
@@ -58,7 +58,10 @@ void bacct_add_tsk(struct taskstats *stats, struct task_struct *tsk)
stats->ac_uid = tsk->uid;
stats->ac_gid = tsk->gid;
stats->ac_pid = tsk->pid;
- stats->ac_ppid = (tsk->parent) ? tsk->parent->pid : 0;
+ rcu_read_lock();
+ stats->ac_ppid = pid_alive(tsk) ?
+ rcu_dereference(tsk->real_parent)->tgid : 0;
+ rcu_read_unlock();
stats->ac_utime = cputime_to_msecs(tsk->utime) * USEC_PER_MSEC;
stats->ac_stime = cputime_to_msecs(tsk->stime) * USEC_PER_MSEC;
stats->ac_minflt = tsk->min_flt;