Re: [PATCH v2 3/3] mm/vmalloc: skip vmalloc_dump_obj for non-vmalloc addresses

[Uladzislau Rezki <urezki@gmail.com>]

On Mon, Sep 21, 2026 at 09:17:23PM +0800, Ye Liu wrote:
> From: Ye Liu <liuye@kylinos.cn>
> 
> vmalloc_dump_obj() unconditionally searches all vmap nodes even when
> called with a non-vmalloc address (e.g. a slab or stack pointer from
> mem_dump_obj()).  Add an is_vmalloc_or_module_addr() check at the
> entry to avoid the unnecessary per-node trylock and rb-tree traversal.
> 
> Use is_vmalloc_or_module_addr() rather than is_vmalloc_addr() because
> module, BPF, and execmem allocations reside in MODULES_VADDR..MODULES_END
> on x86_64, arm64, and riscv -- outside VMALLOC_START..VMALLOC_END -- but
> are still tracked in the same vmap_nodes rb-tree.
> 
> Signed-off-by: Ye Liu <liuye@kylinos.cn>
> ---
>  mm/vmalloc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 30c610f678dc..d8095b558365 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -5277,6 +5277,9 @@ bool vmalloc_dump_obj(void *object)
>  	unsigned long addr;
>  	unsigned long nr_pages;
>  
> +	if (!is_vmalloc_or_module_addr(object))
> +		return false;
> +
>  	addr = PAGE_ALIGN_DOWN((unsigned long) object);
>  
>  	/*
> 
> -- 
> 2.25.1
>
Do we need this check? If it is not the vmalloc address, we just return
noting. Another question is why do you want is_vmalloc_or_module_addr()?

vmalloc_dump_obj() is about VMALLOC_START..VMALLOC_END, IMO.

There are only two users of it and both rely on the VMALLOC_START..VMALLOC_END
range:

<snip>
*** mm/kasan/report.c:
print_address_description[403] if (!vmalloc_dump_obj(addr))

*** mm/util.c:
mem_dump_obj[1096]             if (vmalloc_dump_obj(object))
<snip>

	if (is_vmalloc_addr(addr)) {
		pr_err("The buggy address belongs to a");
		if (!vmalloc_dump_obj(addr))
			pr_cont(" vmalloc virtual mapping\n");
		page = vmalloc_to_page(addr);
	}

and

<snip>
	if (vmalloc_dump_obj(object))
		return;

	if (is_vmalloc_addr(object))
		type = "vmalloc memory";
<snip>

--
Uladzislau Rezki