Re: [PATCH slab] slab: Disallow kprobes in ___slab_alloc()

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Wed, Sep 17, 2025 at 11:34 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
>
> Ah right, I did add one based on your commit log and this conversation:
>
> +/*
> + * We disallow kprobes in ___slab_alloc() to prevent reentrance
> + *
> + * kmalloc() -> ___slab_alloc() -> local_lock_cpu_slab() protected part of
> + * ___slab_alloc() manipulating c->freelist -> kprobe -> bpf ->
> + * kmalloc_nolock() or kfree_nolock() -> __update_cpu_freelist_fast()
> + * manipulating c->freelist without lock.
> + *
> + * This does not prevent kprobe in functions called from ___slab_alloc() such as
> + * local_lock_irqsave() itself, and that is fine, we only need to protect the
> + * c->freelist manipulation in ___slab_alloc() itself.
> + */
> +NOKPROBE_SYMBOL(___slab_alloc);

Perfect. Short and to the point. Thanks!