netdev - [PATCH v2 bpf-next 1/3] bpf: bump jmp sequence limit

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Message-ID: <20190522031421.2825174-2-ast@kernel.org>
Date:   Tue, 21 May 2019 20:14:19 -0700
From:   Alexei Starovoitov <ast@...nel.org>
To:     <davem@...emloft.net>
CC:     <daniel@...earbox.net>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <kernel-team@...com>
Subject: [PATCH v2 bpf-next 1/3] bpf: bump jmp sequence limit

The limit of 1024 subsequent jumps was causing otherwise valid
programs to be rejected. Bump it to 8192 and make the error more verbose.

Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Acked-by: Andrii Nakryiko <andriin@...com>
---
 kernel/bpf/verifier.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 082f6eefb1c4..4113e829616d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -176,7 +176,7 @@ struct bpf_verifier_stack_elem {
 	struct bpf_verifier_stack_elem *next;
 };
 
-#define BPF_COMPLEXITY_LIMIT_STACK	1024
+#define BPF_COMPLEXITY_LIMIT_JMP_SEQ	8192
 #define BPF_COMPLEXITY_LIMIT_STATES	64
 
 #define BPF_MAP_PTR_UNPRIV	1UL
@@ -782,8 +782,9 @@ static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
 	if (err)
 		goto err;
 	elem->st.speculative |= speculative;
-	if (env->stack_size > BPF_COMPLEXITY_LIMIT_STACK) {
-		verbose(env, "BPF program is too complex\n");
+	if (env->stack_size > BPF_COMPLEXITY_LIMIT_JMP_SEQ) {
+		verbose(env, "The sequence of %d jumps is too complex.\n",
+			env->stack_size);
 		goto err;
 	}
 	return &elem->st;
-- 
2.20.0