From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Fri, 8 Feb 2008 12:19:00 +0000 (-0800)
Subject: ptrace_stop: fix the race with ptrace detach+attach
X-Git-Tag: v2.6.25-rc1~230
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6405f7f4675884b671bee66678e1c2859bdb0e56;p=pandora-kernel.git

ptrace_stop: fix the race with ptrace detach+attach

If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops
tasklist and then changes the ->state from TASK_TRACED to TASK_RUNNING.

This can fool another tracer which attaches to us in between.  Change the
->state under tasklist_lock to ensure that ptrace_check_attach() can't wrongly
succeed.  Also, remove the unnecessary mb().

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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