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Re: [PATCH v3 2/2] xen/common: Add NUMA node id bounds check to page_alloc.c/node_to_scrub
- To: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Tue, 26 Sep 2023 23:47:49 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Timothy Pearson <tpearson@xxxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
- Delivery-date: Tue, 26 Sep 2023 23:48:18 +0000
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- Thread-topic: [PATCH v3 2/2] xen/common: Add NUMA node id bounds check to page_alloc.c/node_to_scrub
Hi,
> On Sep 27, 2023, at 06:37, Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
> wrote:
>
> When building for Power with CONFIG_DEBUG unset, a compiler error gets
> raised inside page_alloc.c's node_to_scrub function:
>
> common/page_alloc.c: In function 'node_to_scrub.part.0':
> common/page_alloc.c:1217:29: error: array subscript 1 is above array
> bounds of 'long unsigned int[1]' [-Werror=array-bounds]
> 1217 | if ( node_need_scrub[node] )
>
> It appears that this is a false positive, given that in practice
> cycle_node should never return a node ID >= MAX_NUMNODES as long as the
> architecture's node_online_map is properly defined and initialized, so
> this additional bounds check is only to satisfy GCC.
>
> Signed-off-by: Shawn Anastasio <sanastasio@xxxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
I am seeing some discussions going on about this patch, but once this
is patch is ready for merge please feel free to add:
Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
> ---
> v2: Add comment to explain the bounds check.
>
> xen/common/page_alloc.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
> index 35d9a26fa6..9b5df74fdd 100644
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -1211,6 +1211,14 @@ static unsigned int node_to_scrub(bool get_node)
> } while ( !cpumask_empty(&node_to_cpumask(node)) &&
> (node != local_node) );
>
> + /*
> + * In practice `node` will always be within MAX_NUMNODES, but GCC
> can't
> + * always see that, so an explicit check is necessary to avoid
> tripping
> + * its out-of-bounds array access warning (-Warray-bounds).
> + */
> + if ( node >= MAX_NUMNODES )
> + break;
> +
> if ( node == local_node )
> break;
>
> --
> 2.30.2
>
>
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