Hello Van Giang,
On Fri, Aug 09, 2024 at 06:21:42AM GMT, VanGiang Nguyen wrote:
> When submitting more than 2^32 padata objects to padata_do_serial, the
> current sorting implementation incorrectly sorts padata objects with
> overflowed seq_nr, causing them to be placed before existing objects in
> the reorder list. This leads to a deadlock in the serialization process
> as padata_find_next cannot match padata->seq_nr and pd->processed
> because the padata instance with overflowed seq_nr will be selected
> next.
>
> To fix this, we use an unsigned integer wrap around to correctly sort
> padata objects in scenarios with integer overflow.
>
Could use a Fixes tag like this one:
Fixes: bfde23ce200e ("padata: unbind parallel jobs from specific CPUs")
Otherwise looks good, thanks.
Acked-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> Co-developed-by: Christian Gafert <christian.gafert@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Christian Gafert <christian.gafert@xxxxxxxxxxxxxxxxx>
> Co-developed-by: Max Ferger <max.ferger@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Max Ferger <max.ferger@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Van Giang Nguyen <vangiang.nguyen@xxxxxxxxxxxxxxxxx>
> ---
> kernel/padata.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/padata.c b/kernel/padata.c
> index 53f4bc912712..222bccd0c96b 100644
> --- a/kernel/padata.c
> +++ b/kernel/padata.c
> @@ -404,7 +404,8 @@ void padata_do_serial(struct padata_priv *padata)
> /* Sort in ascending order of sequence number. */
> list_for_each_prev(pos, &reorder->list) {
> cur = list_entry(pos, struct padata_priv, list);
> - if (cur->seq_nr < padata->seq_nr)
> + /* Compare by difference to consider integer wrap around */
> + if ((signed int)(cur->seq_nr - padata->seq_nr) < 0)
> break;
> }
> list_add(&padata->list, pos);
> --
> 2.34.1
>
