Messages in this thread | | | Date | Fri, 20 Jan 2017 00:04:17 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [RFC][PATCH] x86: Verify access_ok() context |
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Frank.
On Thu, 19 Jan 2017, Frank Ch. Eigler wrote: > > Well, if you are not in thread context then the check is pointless: > > __range_not_ok(addr, size, user_addr_max()) > > and: > > #define user_addr_max() (current->thread.addr_limit.seg) > > > > So what guarantees when you are not in context of current, i.e. in thread > > context, that the addr/size which is checked against the limits of current > > actually belongs to current? > > We're probably in task context in that there is a valid current(), but
current is always accessible no matter in which context you are - task, softirq, hardirq, nmi ...
> running with preemption and/or interrupts and/or pagefaults disabled > at that point, so in_task() objects.
As Peter explained, neither preempt disable nor interrupt disable not pagefault disabled have any influence on in_task(). It merily checks the context: !in_softirq() && !in_hardirq() && !in_nmi().
So that warning happens definitely not from task context.
Care to share the code?
Thanks,
tglx
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