This is a note to let you know that I've just added the patch titled
ptrace: use safer wake up on ptrace_detach()
to the 2.6.36-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ptrace-use-safer-wake-up-on-ptrace_detach.patch
and it can be found in the queue-2.6.36 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 01e05e9a90b8f4c3997ae0537e87720eb475e532 Mon Sep 17 00:00:00 2001
From: Tejun Heo <[email protected]>
Date: Thu, 10 Feb 2011 15:01:22 -0800
Subject: ptrace: use safer wake up on ptrace_detach()
From: Tejun Heo <[email protected]>
commit 01e05e9a90b8f4c3997ae0537e87720eb475e532 upstream.
The wake_up_process() call in ptrace_detach() is spurious and not
interlocked with the tracee state. IOW, the tracee could be running or
sleeping in any place in the kernel by the time wake_up_process() is
called. This can lead to the tracee waking up unexpectedly which can be
dangerous.
The wake_up is spurious and should be removed but for now reduce its
toxicity by only waking up if the tracee is in TRACED or STOPPED state.
This bug can possibly be used as an attack vector. I don't think it
will take too much effort to come up with an attack which triggers oops
somewhere. Most sleeps are wrapped in condition test loops and should
be safe but we have quite a number of places where sleep and wakeup
conditions are expected to be interlocked. Although the window of
opportunity is tiny, ptrace can be used by non-privileged users and with
some loading the window can definitely be extended and exploited.
Signed-off-by: Tejun Heo <[email protected]>
Acked-by: Roland McGrath <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/ptrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -313,7 +313,7 @@ int ptrace_detach(struct task_struct *ch
child->exit_code = data;
dead = __ptrace_detach(current, child);
if (!child->exit_state)
- wake_up_process(child);
+ wake_up_state(child, TASK_TRACED | TASK_STOPPED);
}
write_unlock_irq(&tasklist_lock);
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.36/ptrace-use-safer-wake-up-on-ptrace_detach.patch
queue-2.6.36/pci-pci-stub-ignore-zero-length-id-parameters.patch
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