linux-kernel - Re: [PATCH bpf 1/1] bpf: test_run: fix ctx leak in bpf_prog_test_run

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Message-ID: <aO5ZQ9Kgd35nWNod@krava>
Date: Tue, 14 Oct 2025 16:08:03 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Shardul Bankar <shardulsb08@...il.com>
Cc: bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	"open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf 1/1] bpf: test_run: fix ctx leak in
 bpf_prog_test_run_xdp error path

On Tue, Oct 14, 2025 at 05:30:37PM +0530, Shardul Bankar wrote:
> Fix a memory leak in bpf_prog_test_run_xdp() where the context buffer
> allocated by bpf_ctx_init() is not freed when the function returns early
> due to a data size check.
> 
> On the failing path:
>   ctx = bpf_ctx_init(...);
>   if (kattr->test.data_size_in - meta_sz < ETH_HLEN)
>       return -EINVAL;
> 
> The early return bypasses the cleanup label that kfree()s ctx, leading to a
> leak detectable by kmemleak under fuzzing. Change the return to jump to the
> existing free_ctx label.
> 
> Fixes: fe9544ed1a2e ("bpf: Support specifying linear xdp packet data size for BPF_PROG_TEST_RUN")
> Reported-by: BPF Runtime Fuzzer (BRF)
> Signed-off-by: Shardul Bankar <shardulsb08@...il.com>

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

jirka

> ---
>  net/bpf/test_run.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index dfb03ee0bb62..1782e83de2cb 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -1269,7 +1269,7 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
>  		goto free_ctx;
>  
>  	if (kattr->test.data_size_in - meta_sz < ETH_HLEN)
> -		return -EINVAL;
> +		goto free_ctx;
>  
>  	data = bpf_test_init(kattr, linear_sz, max_linear_sz, headroom, tailroom);
>  	if (IS_ERR(data)) {
> -- 
> 2.34.1
>