On 01/10/2014 03:06 PM, Peter Zijlstra wrote:
:-) Something like this perhaps? --- Subject: x86, mm: Allow double faults from interrupts Waiman managed to trigger a PMI while in a emulate_vsyscall() fault, the PMI in turn managed to trigger a fault while obtaining a stack trace. This triggered the double fault logic and killed the process dead. Fix this by explicitly excluding interrupts from the double fault logic. Reported-by: Waiman Long<[email protected]> Signed-off-by: Peter Zijlstra<[email protected]> --- arch/x86/mm/fault.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 9ff85bb8dd69..4c8e32986aad 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -641,6 +641,20 @@ no_context(struct pt_regs *regs, unsigned long error_code, /* Are we prepared to handle this kernel fault? */ if (fixup_exception(regs)) { + /* + * Any interrupt that takes a fault gets the fixup. This + * makes the below double fault logic only apply to a + * task double faulting from task context. + */ + if (in_interrupt()) + return; + + /* + * Per the above we're !in_interrupt(), aka. task context. + * + * In this case we need to make sure we're not double faulting + * through the emulate_vsyscall() logic. + */ if (current_thread_info()->sig_on_uaccess_error&& signal) { tsk->thread.trap_nr = X86_TRAP_PF; tsk->thread.error_code = error_code | PF_USER; @@ -649,6 +663,10 @@ no_context(struct pt_regs *regs, unsigned long error_code, /* XXX: hwpoison faults will set the wrong code. */ force_sig_info_fault(signal, si_code, address, tsk, 0); } + + /* + * Barring that, we can do the fixup and be happy. + */ return; }
Are you going to send out an official patch to fix this problem? I really like to see it merged into 3.13 before it is released.
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