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

Jiri Olsa
2024-08-14T07:05:08Z

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@vger.kernel.org
> Fixes: 89ae89f53d20 ("bpf: Add multi uprobe link")
> Reported-by: syzbot+f7a1c2c2711e4a780f19@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/000000000000382d39061f59f2dd@google.com/
> Tested-by: syzbot+f7a1c2c2711e4a780f19@syzkaller.appspotmail.com
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

thanks for fixing this

Acked-by: Jiri Olsa <jolsa@kernel.org>

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
>
>