linux-kernel - Re: [PATCH bpf-next v2 05/13] resolve_btfids: Support for KF_IMPLICIT

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Message-Id: <d2f3a4f9eb847c74dbc7e584bfcff55bdde5c4c20382f77339299e1cc95e4102@mail.kernel.org>
Date: Fri, 16 Jan 2026 20:39:43 +0000 (UTC)
From: bot+bpf-ci@...nel.org
To: ihor.solodrai@...ux.dev,ast@...nel.org,daniel@...earbox.net,andrii@...nel.org,martin.lau@...ux.dev,eddyz87@...il.com
Cc: yatsenko@...a.com,tj@...nel.org,alan.maguire@...cle.com,bentiss@...nel.org,jikos@...nel.org,ameryhung@...il.com,bpf@...r.kernel.org,linux-kernel@...r.kernel.org,linux-input@...r.kernel.org,sched-ext@...ts.linux.dev,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 v2 05/13] resolve_btfids: Support for KF_IMPLICIT_ARGS

> diff --git a/tools/bpf/resolve_btfids/main.c b/tools/bpf/resolve_btfids/main.c
> index 1fcf37af6764..b83316359cfd 100644
> --- a/tools/bpf/resolve_btfids/main.c
> +++ b/tools/bpf/resolve_btfids/main.c

[ ... ]

> +struct btf2btf_context {
> +	struct btf *btf;
> +	u32 *decl_tags;
> +	u32 nr_decl_tags;
> +	struct kfunc *kfuncs;
> +	u32 nr_kfuncs;
> +};

[ ... ]

> +static int collect_decl_tags(struct btf2btf_context *ctx)
> +{
> +	const u32 type_cnt = btf__type_cnt(ctx->btf);
> +	struct btf *btf = ctx->btf;
> +	const struct btf_type *t;
> +	u32 *tags, *tmp;
> +	u32 nr_tags = 0;
> +
> +	tags = malloc(type_cnt * sizeof(u32));
> +	if (!tags)
> +		return -ENOMEM;

[ ... ]

> +	tmp = realloc(tags, nr_tags * sizeof(u32));
> +	if (!tmp) {
> +		free(tags);
> +		return -ENOMEM;
> +	}
> +
> +	ctx->decl_tags = tmp;
> +	ctx->nr_decl_tags = nr_tags;
> +
> +	return 0;
> +}

[ ... ]

> +static s64 collect_kfuncs(struct object *obj, struct btf2btf_context *ctx)
> +{
> +	struct kfunc *kfunc, *kfuncs, *tmp;

[ ... ]

> +	kfuncs = malloc(ctx->nr_decl_tags * sizeof(*kfuncs));
> +	if (!kfuncs)
> +		return -ENOMEM;

[ ... ]

> +	tmp = realloc(kfuncs, nr_kfuncs * sizeof(*kfuncs));
> +	if (!tmp) {
> +		free(kfuncs);
> +		return -ENOMEM;
> +	}
> +
> +	ctx->kfuncs = tmp;
> +	ctx->nr_kfuncs = nr_kfuncs;
> +
> +	return 0;
> +}
> +
> +static int build_btf2btf_context(struct object *obj, struct btf2btf_context *ctx)
> +{
> +	int err;
> +
> +	ctx->btf = obj->btf;
> +
> +	err = collect_decl_tags(ctx);
> +	if (err) {
> +		pr_err("ERROR: resolve_btfids: failed to collect decl tags from BTF\n");
> +		return err;
> +	}
> +
> +	err = collect_kfuncs(obj, ctx);
> +	if (err) {
> +		pr_err("ERROR: resolve_btfids: failed to collect kfuncs from BTF\n");
> +		return err;
                  ^^^^

When collect_kfuncs() fails here, ctx->decl_tags has already been allocated
by collect_decl_tags() but is not freed before returning. Should this error
path call free(ctx->decl_tags)?

> +	}
> +
> +	return 0;
> +}

[ ... ]

> +static int btf2btf(struct object *obj)
> +{
> +	struct btf2btf_context ctx = {};
> +	int err;
> +
> +	err = build_btf2btf_context(obj, &ctx);
> +	if (err)
> +		return err;
> +
> +	for (u32 i = 0; i < ctx.nr_kfuncs; i++) {
> +		struct kfunc *kfunc = &ctx.kfuncs[i];
> +
> +		if (!(kfunc->flags & KF_IMPLICIT_ARGS))
> +			continue;
> +
> +		err = process_kfunc_with_implicit_args(&ctx, kfunc);
> +		if (err)
> +			return err;
> +	}
> +
> +	return 0;
> +}
          ^^^^

ctx.decl_tags and ctx.kfuncs are allocated during build_btf2btf_context()
but are never freed on any return path from btf2btf(). While this may be
acceptable for a short-lived build tool where the OS reclaims memory on
exit, should cleanup be added for consistency with the rest of the code
which carefully frees allocations?


---
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CI run summary: https://github.com/kernel-patches/bpf/actions/runs/21079944982