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SubjectRe: [PATCH] mm: add NULL check to avoid potential NULL pointer dereference
On Tue 30-05-17 16:24:36, Gustavo A. R. Silva wrote:
> NULL check at line 1226: if (!pgdat), implies that pointer pgdat
> might be NULL.
> Function rollback_node_hotadd() dereference this pointer.
> Add NULL check to avoid a potential NULL pointer dereference.

The changelog is quite cryptic to be honest. Well the code is as well
but what do you say about the following replacement.

"
If a new pgdat has to be allocated in add_memory_resource
and the initialization fails for some reason we have to
rollback_node_hotadd. This, however, assumes that pgdat allocation
itself is successful which cannot be assumed. Add a check for pgdat
to cover that case and skip rollback_node_hotadd altogether because
there is nothing to roll back.

This has been pointed out by coverity.
"
>
> Addresses-Coverity-ID: 1369133
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 599c675..ea3bc3e 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1273,7 +1273,7 @@ int __ref add_memory_resource(int nid, struct resource *res, bool online)
>
> error:
> /* rollback pgdat allocation and others */
> - if (new_pgdat)
> + if (new_pgdat && pgdat)
> rollback_node_hotadd(nid, pgdat);
> memblock_remove(start, size);
>
> --
> 2.5.0
>
> --
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--
Michal Hocko
SUSE Labs

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