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| author | Oleg Nesterov <oleg@tv-sign.ru> | 2006-10-28 10:38:50 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-10-28 11:30:54 -0700 |
| commit | 05d5bcd60e8202e5c7b28cf61186043a4d612623 (patch) | |
| tree | 7dccbeeb9d0b41103d70f89aae5eb6850f2f788c | |
| parent | fca178c0c6e8d52a1875be36b070f30884ebfae9 (diff) | |
| download | linux-05d5bcd60e8202e5c7b28cf61186043a4d612623.tar.gz linux-05d5bcd60e8202e5c7b28cf61186043a4d612623.tar.bz2 linux-05d5bcd60e8202e5c7b28cf61186043a4d612623.zip | |
[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>
| -rw-r--r-- | kernel/tsacct.c | 7 |
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; |