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Re: [Xen-devel] [PATCH v2 03/12] x86/IRQ: avoid UB (or worse) in trace_irq_mask()


  • To: Jan Beulich <JBeulich@xxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Mon, 13 May 2019 11:42:41 +0100
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  • Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
  • Delivery-date: Mon, 13 May 2019 10:42:50 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 5/8/19 2:07 PM, Jan Beulich wrote:
> Dynamically allocated CPU mask objects may be smaller than cpumask_t, so
> copying has to be restricted to the actual allocation size. This is
> particulary important since the function doesn't bail early when tracing
> is not active, so even production builds would be affected by potential
> misbehavior here.
> 
> Take the opportunity and also
> - use initializers instead of assignment + memset(),
> - constify the cpumask_t input pointer,
> - u32 -> uint32_t.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> v2: New.
> ---
> TBD: I wonder whether the function shouldn't gain an early tb_init_done
>      check, like many other trace_*() have.

Yeah, avoiding these memcopies when tracing is not enabled seems like a
good thing.

Either way:

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>

> 
> George, despite your general request to be copied on entire series
> rather than individual patches, I thought it would be better to copy
> you on just this one (for its tracing aspect), as the patch here is
> independent of the rest of the series, but at least one later patch
> depends on the parameter constification done here.

Yes, I think in this case this was the easiest thing for me.  Thanks. :-)

 -George

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