Messages in this thread | | | Date | Thu, 19 Jan 2017 21:50:36 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [RFC][PATCH] x86: Verify access_ok() context |
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On Thu, 19 Jan 2017, Frank Ch. Eigler wrote:
> Hi, Thomas - > > On Thu, Jan 19, 2017 at 07:12:48PM +0100, Thomas Gleixner wrote: > > [...] > > It does matter very much, because the fact that the warning triggers tells > > me that it's placed in code which is NOT executed in task context. > > [...] > > We are not papering over problems. > > Understood. We were interpreting the comments around access_ok to > mean that the underlying hazard condition was different (stricter) > than in_task(). If the warning could be made to match that hazard > condition more precisely, then safe but non-in_task() callers can use > access_ok() without the warning.
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?
I assume this is about systemtap modules. Can you please explain what you are trying to achieve? I guess you know that you actually access current, but then we need a seperate special function and not relaxing of the checks.
Thanks,
tglx
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