From: Arnd Bergmann <arnd@arndb.de>
Date: Thu, 2 Nov 2017 12:05:52 +0100
Subject: bpf: fix out-of-bounds access warning in bpf_check
Patch-mainline: v4.15-rc1
Git-commit: eba0c929d1d0f16c4b03628b7bf8ce363b9e5c9a
References: bsc#1109837

The bpf_verifer_ops array is generated dynamically and may be
empty depending on configuration, which then causes an out
of bounds access:

kernel/bpf/verifier.c: In function 'bpf_check':
kernel/bpf/verifier.c:4320:29: error: array subscript is above array bounds [-Werror=array-bounds]

This adds a check to the start of the function as a workaround.
I would assume that the function is never called in that configuration,
so the warning is probably harmless.

Fixes: 00176a34d9e2 ("bpf: remove the verifier ops from program structure")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/verifier.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4334,6 +4334,10 @@ int bpf_check(struct bpf_prog **prog, un
 	struct bpf_verifer_log *log;
 	int ret = -EINVAL;
 
+	/* no program is valid */
+	if (ARRAY_SIZE(bpf_verifier_ops) == 0)
+		return -EINVAL;
+
 	/* 'struct bpf_verifier_env' can be global, but since it's not small,
 	 * allocate/free it every time bpf_check() is called
 	 */