bpf: fix out-of-bounds access warning in bpf_check

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: 3136dfbf88df ("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>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5f3799dcba019d4b44be878ae9c783e67b27ee9c..ab5aa549766650cdbbe6e42345ef90895f7d3e3b 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4474,6 +4474,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
        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
         */