From 80a58d02559465b0ea403ff91c8bca9a733b1b0d Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Tue, 30 May 2017 13:31:30 -0700 Subject: [PATCH] bpf: reconcile bpf_tail_call and stack_depth The next set of patches will take advantage of stack_depth tracking, so make sure that the program that does bpf_tail_call() has stack depth large enough for the callee. We could have tracked the stack depth of the prog_array owner program and only allow insertion of the programs with stack depth less than the owner, but it will break existing applications. Some of them have trivial root bpf program that only does multiple bpf_tail_calls and at init time the prog array is empty. In the future we may add a flag to do such tracking optionally, but for now play simple and safe. Signed-off-by: Alexei Starovoitov Acked-by: Daniel Borkmann Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d96f27ff9f6f..14ccb0759fa4 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3470,6 +3470,7 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) * the program array. */ prog->cb_access = 1; + env->prog->aux->stack_depth = MAX_BPF_STACK; /* mark bpf_tail_call as different opcode to avoid * conditional branch in the interpeter for every normal