Messages in this thread | | | Date | Fri, 2 Nov 2018 12:12:24 -0400 (EDT) | From | Nicolas Pitre <> | Subject | Re: [PATCH v2] gpiolib: Fix possible use after free on label |
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On Fri, 2 Nov 2018, Linus Walleij wrote:
> On Thu, Nov 1, 2018 at 4:27 PM Linus Walleij <linus.walleij@linaro.org> wrote: > > On Thu, Nov 1, 2018 at 2:13 PM Muchun Song <smuchun@gmail.com> wrote: > > > > > gpiod_request_commit() copies the pointer to the label passed as > > > an argument only to be used later. But there's a chance the caller > > > could immediately free the passed string(e.g., local variable). > > > This could trigger a use after free when we use gpio label(e.g., > > > gpiochip_unlock_as_irq(), gpiochip_is_requested()). > > > > > > To be on the safe side: duplicate the string with kstrdup_const() > > > so that if an unaware user passes an address to a stack-allocated > > > buffer, we won't get the arbitrary label. > > > > > > Also fix gpiod_set_consumer_name(). > > > > > > Signed-off-by: Muchun Song <smuchun@gmail.com> > > > > I am still a bit worried about the kstrdup_const() that this > > introduces. > > Forget it. I realized after actually reading the code > for kstrdup_const() that it really does exactly > what we want. > > I should stop assuming things are syntactic sugar > in the kernel, we have some really smart people > working with it...
I didn't know about kstrdup_const() either before just now.
If the device tree lands in the kernel rodata area then all is fine. I don't know enough about the actual DT processing to be sure though.
Nicolas
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