From a34acf30b19bc4ee3ba2f1082756ea2604c19138 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Wed, 26 Jun 2024 16:03:30 +0200 Subject: [PATCH] mm: vmalloc: check if a hash-index is in cpu_possible_mask 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@gmail.com Fixes: 062eacf57ad9 ("mm: vmalloc: remove a global vmap_blocks xarray") Reported-by: Nick Bowler Closes: https://lore.kernel.org/linux-kernel/ZntjIE6msJbF8zTa@MiWiFi-R3L-srv/T/ Signed-off-by: Uladzislau Rezki (Sony) Reviewed-by: Baoquan He Cc: Christoph Hellwig Cc: Hailong.Liu Cc: Oleksiy Avramchenko Cc: Signed-off-by: Andrew Morton --- mm/vmalloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d0cbdd7c1e5b..e34ea860153f 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2543,7 +2543,15 @@ static DEFINE_PER_CPU(struct vmap_block_queue, vmap_block_queue); 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; }