6.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Olsa olsajiri@gmail.com
[ Upstream commit e4414b01c1cd9887bbde92f946c1ba94e40d6d64 ]
kernel test robot reported verifier bug [1] where the helper func pointer could be NULL due to disabled config option.
As Alexei suggested we could check on that in get_helper_proto directly. Marking tail_call helper func with BPF_PTR_POISON, because it is unused by design.
[1] https://lore.kernel.org/oe-lkp/202507160818.68358831-lkp@intel.com
Reported-by: kernel test robot oliver.sang@intel.com Reported-by: syzbot+a9ed3d9132939852d0df@syzkaller.appspotmail.com Suggested-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Jiri Olsa jolsa@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Paul Chaignon paul.chaignon@gmail.com Acked-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20250814200655.945632-1-jolsa@kernel.org Closes: https://lore.kernel.org/oe-lkp/202507160818.68358831-lkp@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/core.c | 5 ++++- kernel/bpf/verifier.c | 2 +- 2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 829f0792d8d83..17e5cf18da1ef 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -3013,7 +3013,10 @@ EXPORT_SYMBOL_GPL(bpf_event_output);
/* Always built-in helper functions. */ const struct bpf_func_proto bpf_tail_call_proto = { - .func = NULL, + /* func is unused for tail_call, we set it to pass the + * get_helper_proto check + */ + .func = BPF_PTR_POISON, .gpl_only = false, .ret_type = RET_VOID, .arg1_type = ARG_PTR_TO_CTX, diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4fd89659750b2..d6782efd25734 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11206,7 +11206,7 @@ static int get_helper_proto(struct bpf_verifier_env *env, int func_id, return -EINVAL;
*ptr = env->ops->get_func_proto(func_id, env->prog); - return *ptr ? 0 : -EINVAL; + return *ptr && (*ptr)->func ? 0 : -EINVAL; }
static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,