netdev - Re: [PATCH bpf 2/3] bpf: zero out build_id for BPF_STACK_BUILD_ID

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Message-ID: <4EFF086F-81EB-48BE-AC78-F8DB8B29003F@fb.com>
Date:   Wed, 16 Jan 2019 17:48:48 +0000
From:   Song Liu <songliubraving@...com>
To:     Stanislav Fomichev <sdf@...gle.com>
CC:     Netdev <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>
Subject: Re: [PATCH bpf 2/3] bpf: zero out build_id for BPF_STACK_BUILD_ID_IP



> On Jan 15, 2019, at 2:54 PM, Stanislav Fomichev <sdf@...gle.com> wrote:
> 
> When returning BPF_STACK_BUILD_ID_IP from stack_map_get_build_id_offset,
> make sure that build_id field is empty. Since we are using percpu
> free list, there is a possibility that we might reuse some previous
> bpf_stack_build_id with non-zero build_id.
> 
> Fixes: 615755a77b24 ("bpf: extend stackmap to save binary_build_id+offset instead of address")
> Signed-off-by: Stanislav Fomichev <sdf@...gle.com>

Acked-by: Song Liu <songliubraving@...com>

> ---
> kernel/bpf/stackmap.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index 8975d1768dcb..f4b57c68c45f 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -315,6 +315,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
> 		for (i = 0; i < trace_nr; i++) {
> 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> 			id_offs[i].ip = ips[i];
> +			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
> 		}
> 		return;
> 	}
> @@ -325,6 +326,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
> 			/* per entry fall back to ips */
> 			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
> 			id_offs[i].ip = ips[i];
> +			memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE);
> 			continue;
> 		}
> 		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i]
> -- 
> 2.20.1.97.g81188d93c3-goog
>