From: Tejun Heo <[email protected]> ------------------- This is a commit scheduled for the next v2.6.34 longterm release. If you see a problem with using this for longterm, please comment. -------------------
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: Paul Gortmaker <[email protected]> --- kernel/ptrace.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 42ad8ae..b7b491e 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -315,7 +315,7 @@ 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); -- 1.7.4.4 _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
