The patch titled Subject: mm: vmalloc: check if a hash-index is in cpu_possible_mask has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-vmalloc-check-if-a-hash-index-is-in-cpu_possible_mask.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: "Uladzislau Rezki (Sony)" urezki@gmail.com Subject: mm: vmalloc: check if a hash-index is in cpu_possible_mask Date: Wed, 26 Jun 2024 16:03:30 +0200

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 nbowler@draconx.ca Closes: https://lore.kernel.org/linux-kernel/ZntjIE6msJbF8zTa@MiWiFi-R3L-srv/T/ Signed-off-by: Uladzislau Rezki (Sony) urezki@gmail.com Cc: Baoquan He bhe@redhat.com Cc: Christoph Hellwig hch@infradead.org Cc: Hailong.Liu hailong.liu@oppo.com Cc: Oleksiy Avramchenko oleksiy.avramchenko@sony.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/vmalloc.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/mm/vmalloc.c~mm-vmalloc-check-if-a-hash-index-is-in-cpu_possible_mask +++ a/mm/vmalloc.c @@ -2543,7 +2543,15 @@ 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 -mm which might be from urezki@gmail.com are

mm-vmalloc-check-if-a-hash-index-is-in-cpu_possible_mask.patch