From: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> commit a34acf30b19bc4ee3ba2f1082756ea2604c19138 upstream. The problem is that there are systems where cpu_possible_mask has gaps between set CPUs, for example SPARC. In this scenario addr_to_vb_xa() hash function can return an index which accesses to not-possible and not setup CPU area using per_cpu() macro. This results in an oops on SPARC. A per-cpu vmap_block_queue is also used as hash table, incorrectly assuming the cpu_possible_mask has no gaps. Fix it by adjusting an index to a next possible CPU. Link: https://lkml.kernel.org/r/20240626140330.89836-1-urezki@xxxxxxxxx Fixes: 062eacf57ad9 ("mm: vmalloc: remove a global vmap_blocks xarray") Reported-by: Nick Bowler <nbowler@xxxxxxxxxx> Closes: https://lore.kernel.org/linux-kernel/ZntjIE6msJbF8zTa@MiWiFi-R3L-srv/T/ Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Reviewed-by: Baoquan He <bhe@xxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Cc: Hailong.Liu <hailong.liu@xxxxxxxx> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/vmalloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1984,7 +1984,15 @@ static DEFINE_PER_CPU(struct vmap_block_ static struct xarray * addr_to_vb_xa(unsigned long addr) { - int index = (addr / VMAP_BLOCK_SIZE) % num_possible_cpus(); + int index = (addr / VMAP_BLOCK_SIZE) % nr_cpu_ids; + + /* + * Please note, nr_cpu_ids points on a highest set + * possible bit, i.e. we never invoke cpumask_next() + * if an index points on it which is nr_cpu_ids - 1. + */ + if (!cpu_possible(index)) + index = cpumask_next(index, cpu_possible_mask); return &per_cpu(vmap_block_queue, index).vmap_blocks; } Patches currently in stable-queue which might be from urezki@xxxxxxxxx are queue-6.6/mm-vmalloc-check-if-a-hash-index-is-in-cpu_possible_mask.patch
