netdev - Re: [PATCH bpf-next v5 4/7] libbpf: Add support for associating BPF program with struct

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Message-Id: <b4c70f2af7001ee36b8d3702f280ca11e3ba281ba29cdcb63434ee28e0a8060a@mail.kernel.org>
Date: Tue,  4 Nov 2025 17:54:53 +0000 (UTC)
From: bot+bpf-ci@...nel.org
To: ameryhung@...il.com,bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,alexei.starovoitov@...il.com,andrii@...nel.org,daniel@...earbox.net,tj@...nel.org,martin.lau@...nel.org,ameryhung@...il.com,kernel-team@...a.com,ast@...nel.org,andrii@...nel.org,daniel@...earbox.net,martin.lau@...nel.org,eddyz87@...il.com,yonghong.song@...ux.dev,clm@...a.com,ihor.solodrai@...ux.dev
Subject: Re: [PATCH bpf-next v5 4/7] libbpf: Add support for associating BPF program with struct_ops

> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index fbe74686c..260e1feaa 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c

[ ... ]

> @@ -13891,6 +13891,36 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
>  	return 0;
>  }
>
> +int bpf_program__assoc_struct_ops(struct bpf_program *prog, struct bpf_map *map,
> +				  struct bpf_prog_assoc_struct_ops_opts *opts)
> +{
> +	int prog_fd;
> +
> +	prog_fd = bpf_program__fd(prog);
> +	if (prog_fd < 0) {
> +		pr_warn("prog '%s': can't associate BPF program without FD (was it loaded?)\n",
> +			prog->name);
                     ^^^^^^^^^^

Can prog be NULL here? If bpf_program__fd() returns -EINVAL because prog
was NULL, this dereferences prog->name without a NULL check. Looking at
bpf_program__set_attach_target() just above, it checks "if (!prog)"
before any dereferences.

> +		return -EINVAL;
> +	}
> +
> +	if (prog->type == BPF_PROG_TYPE_STRUCT_OPS) {
           ^^^^^^^^^^

Same issue - prog->type is dereferenced without verifying prog is not
NULL.

> +		pr_warn("prog '%s': can't associate struct_ops program\n", prog->name);
> +		return -EINVAL;
> +	}
> +
> +	if (map->fd < 0) {
           ^^^^^^

Can map be NULL? There's no NULL check before dereferencing map->fd.
Other map APIs like bpf_map__fd() and bpf_map__name() check for NULL
before use.

> +		pr_warn("map '%s': can't associate BPF map without FD (was it created?)\n", map->name);
> +		return -EINVAL;
> +	}
> +
> +	if (!bpf_map__is_struct_ops(map)) {
> +		pr_warn("map '%s': can't associate non-struct_ops map\n", map->name);
> +		return -EINVAL;
> +	}
> +
> +	return bpf_prog_assoc_struct_ops(prog_fd, map->fd, opts);
> +}
> +


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/19077679684