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SubjectRe: [PATCH v5 10/11] vsprintf: WARN() on invalid pointer access
On Thu 2018-04-26 10:28:05, Sergey Senozhatsky wrote:
> On (04/25/18 13:12), Petr Mladek wrote:
> [..]
> > /*
> > * This is not a fool-proof test. 99% of the time that this will fault is
> > * due to a bad pointer, not one that crosses into bad memory. Just test
> > @@ -623,8 +626,12 @@ static const char *check_pointer_access(const void *ptr)
> > if (!ptr)
> > return "(null)";
> >
> > - if (probe_kernel_address(ptr, byte))
> > + /* Prevent silent crashes when called in printk_safe context. */
> > + if (probe_kernel_address(ptr, byte)) {
> > + WARN(!panic_on_warn && !test_printf_pointer_access,
> > + "vsprintf: invalid pointer address\n");
> > return "(efault)";
> > + }
>
> Can we have a rate-limited print out here? Or may be even a WARN_ONCE()?
> Yes, printk()-s from check_pointer_access() are OK, printk_safe() helps us,
> but at the same time every single invalid pointer access printk()-message
> will log_store() WARN() extra entries. Theoretically, this can harm. What
> do you think?

I believe that these WARNs will be rare. After all they happen in situations
where the kernel crashed so far.

I suggest to keep it as is for now. We could always ratelimit it later if
needed.

Best Regards,
Petr

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