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authorTejun Heo <tj@kernel.org>2011-02-10 15:01:22 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2011-02-11 16:12:19 -0800
commit01e05e9a90b8f4c3997ae0537e87720eb475e532 (patch)
treee5bace65224c8b026cfd06a28cd00c3f3a69a0c8 /kernel
parentd863b50ab01333659314c2034890cb76d9fdc3c7 (diff)
downloadlinux-linaro-stable-01e05e9a90b8f4c3997ae0537e87720eb475e532.tar.gz
ptrace: use safer wake up on ptrace_detach()
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 <tj@kernel.org> Acked-by: Roland McGrath <roland@redhat.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/ptrace.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 99bbaa3e5b0d..1708b1e2972d 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -313,7 +313,7 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
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);