RE: [PATCH v2] arm/vgic-v2: Fix undefined behavior in vgic_fetch_itargetsr()

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Yes, I committed it. Thank you for the ping.

Cheers,

Stefano

On Wed, 4 Jun 2025, Jahan Murudi wrote:
>  Hi Stefano/Julien,
> 
> This v2 patch was reviewed-by Michal Orzel on 2nd June. Could it be merged?
> 
> Link : 
> https://patchwork.kernel.org/project/xen-devel/patch/20250601163212.2988162-1-jahan.murudi.zg@xxxxxxxxxxx/
> 
> Thanks, 
> Jahan Murudi
> 
> 
> -----Original Message-----
> From: Orzel, Michal <michal.orzel@xxxxxxx> 
> Sent: 02 June 2025 12:24
> To: Jahan Murudi <jahan.murudi.zg@xxxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>; Julien Grall 
> <julien@xxxxxxx>; Bertrand Marquis <bertrand.marquis@xxxxxxx>; Volodymyr 
> Babchuk <volodymyr_babchuk@xxxxxxxx>
> Subject: Re: [PATCH v2] arm/vgic-v2: Fix undefined behavior in 
> vgic_fetch_itargetsr()
> 
> 
> 
> On 01/06/2025 18:32, Jahan Murudi wrote:
> > The current implementation performs left shift operations that may 
> > trigger undefined behavior when the target value is too large. This patch:
> > 
> > 1. Changes the shift from signed (1) to unsigned (1U) to ensure 
> > well-defined
> NIT for the future: Use imperative mood
> 
> >    behavior for all valid target values 2. Maintains identical 
> > functionality while fixing the UBSAN warning
> > 
> > The issue was detected by UBSAN:
> > (XEN) UBSAN: Undefined behaviour in arch/arm/vgic-v2.c:73:56
> > (XEN) left shift of 128 by 24 places cannot be represented in type 'int'
> > (XEN) Xen WARN at common/ubsan/ubsan.c:174
> > 
> > Signed-off-by: Jahan Murudi <jahan.murudi.zg@xxxxxxxxxxx>
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
> 
> ~Michal
> 
> > 
> > ---
> > Changed since v1:
> >  * Added space after subject line
> > ---
> >  xen/arch/arm/vgic-v2.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/xen/arch/arm/vgic-v2.c b/xen/arch/arm/vgic-v2.c index 
> > a19d610178..642407fd5b 100644
> > --- a/xen/arch/arm/vgic-v2.c
> > +++ b/xen/arch/arm/vgic-v2.c
> > @@ -70,7 +70,7 @@ static uint32_t vgic_fetch_itargetsr(struct vgic_irq_rank 
> > *rank,
> >      offset &= ~(NR_TARGETS_PER_ITARGETSR - 1);
> >  
> >      for ( i = 0; i < NR_TARGETS_PER_ITARGETSR; i++, offset++ )
> > -        reg |= (1 << read_atomic(&rank->vcpu[offset])) << (i * 
> > NR_BITS_PER_TARGET);
> > +        reg |= (1U << read_atomic(&rank->vcpu[offset])) << (i * 
> > + NR_BITS_PER_TARGET);
> >  
> >      return reg;
> >  }
> 
>