linux-kernel - [PATCH bpf-next] bpf: Fix a verifier message for alloc size helper arg

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Message-Id: <20210112123913.2016804-1-jackmanb@google.com>
Date:   Tue, 12 Jan 2021 12:39:13 +0000
From:   Brendan Jackman <jackmanb@...gle.com>
To:     bpf@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Florent Revest <revest@...omium.org>,
        linux-kernel@...r.kernel.org, Brendan Jackman <jackmanb@...gle.com>
Subject: [PATCH bpf-next] bpf: Fix a verifier message for alloc size helper arg

The error message here is misleading, the argument will be rejected
unless it is a known constant.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 17270b8404f1..5534e667bdb1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4319,7 +4319,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			err = mark_chain_precision(env, regno);
 	} else if (arg_type_is_alloc_size(arg_type)) {
 		if (!tnum_is_const(reg->var_off)) {
-			verbose(env, "R%d unbounded size, use 'var &= const' or 'if (var < const)'\n",
+			verbose(env, "R%d is not a known constant'\n",
 				regno);
 			return -EACCES;
 		}

base-commit: e22d7f05e445165e58feddb4e40cc9c0f94453bc
-- 
2.30.0.284.gd98b1dd5eaa7-goog