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

[Harry Yoo <harry.yoo@oracle.com>]

On Mon, Sep 15, 2025 at 07:21:40PM -0700, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.org>
> 
> Disallow kprobes in ___slab_alloc() to prevent reentrance:
> kmalloc() -> ___slab_alloc() -> local_lock_irqsave() ->
> kprobe -> bpf -> kmalloc_nolock().
> 
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---

Maybe I'm a bit paranoid, but should we also add this to
all functions that ___slab_alloc() calls?

-- 
Cheers,
Harry / Hyeonggon

>  mm/slub.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index c995f3bec69d..922d47b10c2f 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -45,7 +45,7 @@
>  #include <kunit/test-bug.h>
>  #include <linux/sort.h>
>  #include <linux/irq_work.h>
> -
> +#include <linux/kprobes.h>
>  #include <linux/debugfs.h>
>  #include <trace/events/kmem.h>
>  
> @@ -4697,6 +4697,7 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  
>  	goto load_freelist;
>  }
> +NOKPROBE_SYMBOL(___slab_alloc);
>  
>  /*
>   * A wrapper for ___slab_alloc() for contexts where preemption is not yet
> -- 
> 2.47.3