Please create an account to participate in the Slashdot moderation system


Forgot your password?
Bug Transportation Software The Courts

Stack Overflow Could Explain Toyota Vehicles' Unintended Acceleration 664

New submitter robertchin writes "Michael Barr recently testified in the Bookout v. Toyota Motor Corp lawsuit that the likely cause of unintentional acceleration in the Toyota Camry may have been caused by a stack overflow. Due to recursion overwriting critical data past the end of the stack and into the real time operating system memory area, the throttle was left in an open state and the process that controlled the throttle was terminated. How can users protect themselves from sometimes life endangering software bugs?"
This discussion has been archived. No new comments can be posted.

Stack Overflow Could Explain Toyota Vehicles' Unintended Acceleration

Comments Filter:
  • Re:Wow (Score:5, Interesting)

    by snookerdoodle ( 123851 ) on Friday February 21, 2014 @08:02PM (#46307745)

    I have to admit, that was my first thought as well. :)

  • by Skinkie ( 815924 ) on Friday February 21, 2014 @08:04PM (#46307783) Homepage
    How would a mandatory publication of all code as open source [not suggesting liberal licensing here] work out here? Might converge at a collaborative initiative and will most likely be reviewed by all sort of people.
  • by Anonymous Coward on Friday February 21, 2014 @08:14PM (#46307853)

    Idiot drivers hit the gas pedal instead of the brake and instead of owning up to their incompetence as a drivers, they blame the car instead. The Toyota sudden acceleration problem disproportionately affects the elderly and inexperienced drivers. It also a uniquely an American problem and it occurred during a deep recession where GM and Chrysler were going bankrupt and Americans needed some FUD against Toyota because supporting American car companies was the jingoism of the day. The toyota sudden acceleration is more of a case study of an American moral panic and mass hysteria perpetrated by the media than it was an engineering problem.

  • Not much (Score:5, Interesting)

    by n1ywb ( 555767 ) on Friday February 21, 2014 @08:23PM (#46307909) Homepage Journal
    Honestly, not much, except perhaps demand better software. Better processes, better languages. I'm just hypothesizing here but it might not have happened if they had e.g. followed better development standards like the MISRA C standard, or don't use C at all, use Ada or something. Better QA processes might have caught it before it went into production, e.g. using a dynamic stack profiling tool, input fuzzing, whatever. Fundamentally a system like this should have an independant hardware watchdog timer to at least try and make it fail-safe in the event of a CPU crash. Finally any motor vehicle ought to have a manual cutoff switch wired into the fuel pump or ignition circuit so that when the CPU shits it's bits you can still turn the damn thing off before you crash crash.
  • Re:Go Amish? (Score:5, Interesting)

    by CodeArtisan ( 795142 ) on Friday February 21, 2014 @08:59PM (#46308135)

    Coming from the aerospace industry, you cannot have software that has bugs. And if there was the possibility of a software bug, you have to prove that you can mitigate the effect in hardware. So just to say "software has has risks" isn't an acceptable answer (in my opinion). We have to remember this is not an apples to apples comparison. Just because traditional consumer software always has bugs in it (which are acceptable) doesn't mean they are acceptable in other industries. Considering that the failure puts someone's life at risk, I would think it should be considered unacceptable in automotive industry as well.

    If you want your cars to be as expensive as a 747, then you can attain that goal. I used to work in the automotive industry designing embedded software for engine management systems. At that time, no automotive company would pay more than $100 for the Engine Control Unit. Probably 60% of the code was written to manage failures (both software and hardware), and there were other electronic fail safe mechanisms. But you can't mitigate every possible failure event without introducing costs that would have made the unit orders of magnitude more expensive.

  • Re:Live in a cave (Score:5, Interesting)

    by NiteTrip ( 694597 ) on Friday February 21, 2014 @09:29PM (#46308293)
    I had my car suddenly accelerate on me before. I was driving along and suddenly the pedal felt really strange and it start accelerating, even when I took my foot off the pedal. I turned off the car and pulled over. Turns out the rubber mat I put in to protect the inside of my car from wet/snow had somehow managed to flop on top of the pedal and pushed it down. When I heard about these Toyotas accelerating on their own, it's the first thing I thought of.
  • Re: Live in a cave (Score:4, Interesting)

    by Bobb Sledd ( 307434 ) on Friday February 21, 2014 @09:30PM (#46308303) Homepage

    Ok. it's very real. happened to my father-in-law several times before any news broke of this. so claiming it's the driver is pointless waste of time. now you can actually suggest something helpful.

  • Re:Live in a cave (Score:3, Interesting)

    by Anonymous Coward on Friday February 21, 2014 @09:41PM (#46308399)

    Did they also discover a flaw in the brakes such that they could not overcome the engine power? This was the point of the parent post, I think. Modern cars have sufficient braking force to completely stop the engine even at full throttle. So if the driver is "stepping on the brake really hard," the car should stop in spite of a stuck throttle, unless a simultaneous brake system failure can be demonstrated.

    This same thing happened to Audi in the 1980s and as far as anyone can tell, objectively, it was at most a flaw in pedal placement that made the driver more likely to mistake the gas pedal for the brake while stomping something down to the firewall. They solved it by moving the pedals a little.

    You cannot really go by the driver's self-reported experience alone, when the concern is that the driver may be confused. They may have an extremely firm belief about what happened, and that belief may be mistaken.

  • by phantomfive ( 622387 ) on Friday February 21, 2014 @10:03PM (#46308549) Journal
    I think it was actually two problems. There was the problem reported by Wozniak, where cruise control would start to accelerate, but tapping on the brakes would fix the problem. It was a bug, but it wasn't life-threatening at all.

    Then there is the problem of the car going wildly out of control, unable to stop even when the brakes are applied. That one seems to be a case of foolish driver syndrome.
  • Re:Live in a cave (Score:4, Interesting)

    by JonBoy47 ( 2813759 ) on Friday February 21, 2014 @10:10PM (#46308613)

    Many of these uncontrolled acceleration cases involved hybrid Toyota vehicles. In addition to the electronic throttle, Toyota's Hybrid Synergy Drive uses brake by wire, so the computer can dynamically use any desired combination of regenerative and friction braking, based on the hybrid battery charge state and the severity of the driver's control input on the pedal. These cars also eschew mechanical control for the gear-shift and the push-button ignition switch, relying on interface through the ECU.

    It thus seems entirely plausible that a stack overflow, race condition or other crash/freeze/whatever could result in a wide-open throttle with no brakes and no gear-shift or ignition off control. if this is the case, it represents a epic lack of fail-safe design. It certainly doesn't help prevent operator error when Toyota uses a non-PRNDL shift pattern on their hybrids, to say nothing of the lack of industry standardization of the behavior of push-button ignition.

  • by GrahamCox ( 741991 ) on Friday February 21, 2014 @10:55PM (#46308823) Homepage
    One problem caused by this fault is that if the throttle gets stuck in the open position (the exact amount is redacted from the public record, but it looks to be >30%), then the vacuum assist to the brakes is greatly reduced (after all, normally the throttle closes when you move your foot to the brake pedal, so you get full vacuum assist). The upshot is that the driver would need to apply far more pedal pressure than they're used to to get full braking - combined with the fact that the engine is pulling hard it will feel like the brakes have simultaneously failed. Turning off the ignition might help with the acceleration, but not with replenishing the vacuum assistance.

    There is a lot more to this than simple driver error. Read the court testimony, it's a real eye-opener and in fact a really great read: []
  • Re:Go Amish? (Score:5, Interesting)

    by jrumney ( 197329 ) on Friday February 21, 2014 @11:20PM (#46308921)

    Once upon a time ABS was an exotic tech used only on aircraft. I was impressed when they became a car option.

    In other words, ABS software (and hardware) was very expensive to develop, and only the development budgets of airliners was large enough to cover its development. Once developed, the companies that developed it realized that adapting it for automotive use would be within the budget of luxury car makers, and once it was working there, it became very cheap to adapt for standard cars, as the differences are very minor (in fact it is basically a case of the luxury car makers funding continued improvements, and standard cars getting the previous generation that already has its development paid for).

  • Re: Live in a cave (Score:4, Interesting)

    by Z00L00K ( 682162 ) on Saturday February 22, 2014 @03:23AM (#46309591) Homepage

    It depends on if the ABS and/or brake servo is influenced by the bug and makes it harder to apply the brakes.

    Be aware that most brake servos are using the manifold vacuum to increase the brake force. If the engine gets full throttle the vacuum is soon depleted and a much larger force on the pedal is needed which will be experienced as failing brakes.

  • by AmiMoJo ( 196126 ) * <> on Saturday February 22, 2014 @06:59AM (#46310137) Homepage Journal

    That article demonstrates just how clueless the guys doing the testing were. For example they complain that there "thousands of global variables", but that is actually the normal way to write safety critical firmware since local variables can cause stack overflows. They couldn't read any of the source code comments which were in Japanese either, only get poor machine translations of them.

    Most damning of all though is that actually the skid marks the article claims are evidence of the bug are easily explainable, and indeed Toyota did offer an explanation. If the mat/carpet causes the brake and accelerator pedals to become linked pressing one with of course press the other was well. The driver could not explain why she didn't push the brake pedal hard enough to stop the car (even with max acceleration the brakes will always win over the engine), but Toyota could. The mat that was also pushing the accelerator was preventing her from fully engaging the brakes. The pedal could not be pushed down fully.

    The fix was to change the firmware to stop accelerating when both the accelerator and brake are heavily engaged. So, in actual fact, the supposedly lethally flawed firmware is now saving people from their own stupidity.

"If the code and the comments disagree, then both are probably wrong." -- Norm Schryer