linux-kernel - [PATCH bpf 1/2] bpf: support PTR_TO_MEM{,_OR

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Date:   Tue, 12 Jan 2021 11:14:03 +0200
From:   Gilad Reti <gilad.reti@...il.com>
To:     bpf@...r.kernel.org
Cc:     gilad.reti@...il.com, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH bpf 1/2] bpf: support PTR_TO_MEM{,_OR_NULL} register spilling

Add support for pointer to mem register spilling, to allow the verifier
to track pointer to valid memory addresses. Such pointers are returned
for example by a successful call of the bpf_ringbuf_reserve helper.

This patch was suggested as a solution by Yonghong Song.

The patch was partially contibuted by CyberArk Software, Inc.

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier
support for it")
Signed-off-by: Gilad Reti <gilad.reti@...il.com>
---
 kernel/bpf/verifier.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 17270b8404f1..36af69fac591 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2217,6 +2217,8 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
 	case PTR_TO_RDWR_BUF:
 	case PTR_TO_RDWR_BUF_OR_NULL:
 	case PTR_TO_PERCPU_BTF_ID:
+	case PTR_TO_MEM:
+	case PTR_TO_MEM_OR_NULL:
 		return true;
 	default:
 		return false;
-- 
2.27.0