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Re: [PATCH] x86emul: replace UB shifts

  • To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Fri, 31 Jul 2020 11:50:06 +0100
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  • Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Fri, 31 Jul 2020 10:50:15 +0000
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On 31/07/2020 08:06, Jan Beulich wrote:
> Displacement values can be negative, hence we shouldn't left-shift them.
> While auditing shifts, I noticed a pair of missing parentheses, which
> also get added right here.
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

I'd suggest putting the UBSAN report into the commit message

(XEN) UBSAN: Undefined behaviour in x86_emulate/x86_emulate.c:3482:55
(XEN) left shift of negative value -2

Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Tested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>



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