Re: [PATCH tip/perf/core] bpf: fix use-after-free in bpf_uprobe_multi_link_attach()

[Jiri Olsa]

On Tue, Aug 13, 2024 at 05:25:24PM +0200, Oleg Nesterov wrote:
> If bpf_link_prime() fails, bpf_uprobe_multi_link_attach() goes to the
> error_free label and frees the array of bpf_uprobe's without calling
> bpf_uprobe_unregister().
> 
> This leaks bpf_uprobe->uprobe and worse, this frees bpf_uprobe->consumer
> without removing it from the uprobe->consumers list.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 89ae89f53d20 ("bpf: Add multi uprobe link")
> Reported-by: syzbot+f7a1c2c2711e4a780f19@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://lore.kernel.org/all/000000000000382d39061f59f2dd@xxxxxxxxxx/
> Tested-by: syzbot+f7a1c2c2711e4a780f19@xxxxxxxxxxxxxxxxxxxxxxxxx
> Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

thanks for fixing this

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

jirka

> ---
>  kernel/trace/bpf_trace.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 4e391daafa64..90cd30e9723e 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3484,17 +3484,20 @@ int bpf_uprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
>  						    &uprobes[i].consumer);
>  		if (IS_ERR(uprobes[i].uprobe)) {
>  			err = PTR_ERR(uprobes[i].uprobe);
> -			bpf_uprobe_unregister(uprobes, i);
> -			goto error_free;
> +			link->cnt = i;
> +			goto error_unregister;
>  		}
>  	}
>  
>  	err = bpf_link_prime(&link->link, &link_primer);
>  	if (err)
> -		goto error_free;
> +		goto error_unregister;
>  
>  	return bpf_link_settle(&link_primer);
>  
> +error_unregister:
> +	bpf_uprobe_unregister(uprobes, link->cnt);
> +
>  error_free:
>  	kvfree(uprobes);
>  	kfree(link);
> -- 
> 2.25.1.362.g51ebf55
> 
>