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Date: Thu, 02 Jul 2009 20:40:27 +0800
From: Eugene Teo <>
CC: "Steven M. Christey" <>
Subject: CVE-2009-1388 kernel: do_coredump() vs ptrace_start() deadlock

The OpenVZ Linux kernel team has found deadlock between ptrace and 
coredump code. It affects 2.6.18 but does not affect the upstream kernel.

"ptrace_start() spins waiting for child->state == 
TASK_TRACED/TASK_STOPPED. If we race with the coredumping, we have to 
wait until it completes.

If the tracer participates in coredumping too, we deadlock. 
do_coredump() waits for tracer to exit and report 
complete(mm->core_startup_done), the tracer spins in an endless loop.

Change ptrace_start() to abort if child->mm->core_waiters != 0."



Thanks, Eugene
Eugene Teo / Red Hat Security Response Team

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