fix the "remove task_ppid_nr_ns" commit
commita98fdcef941e107eeabae622d85a1f476f25a160
authorOleg Nesterov <oleg@tv-sign.ru>
Mon, 14 Jan 2008 21:02:37 +0000 (15 00:02 +0300)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Mon, 14 Jan 2008 21:23:00 +0000 (14 13:23 -0800)
tree1702a6e810016eea5e995eb7c91a101688e8c59c
parent4fd3670eb1d3c33e8952cf1e79edbb2d517dcfb5
fix the "remove task_ppid_nr_ns" commit

Commit 84427eaef1fb91704c7112bdb598c810003b99f3 (remove task_ppid_nr_ns)
moved the task_tgid_nr_ns(task->real_parent) outside of lock_task_sighand().
This is wrong, ->real_parent could be freed/reused.

Both ->parent/real_parent point to nothing after __exit_signal() because
we remove the child from ->children list, and thus the child can't be
reparented when its parent exits.

rcu_read_lock() protects ->parent/real_parent, but _only_ if we know it was
valid before we take rcu lock.

Revert this part of the patch.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/proc/array.c