From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D101A2EACE3; Wed, 13 Aug 2025 13:38:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755092325; cv=none; b=HksKEmgQHNLjmbRrUEgvi/AJvfmegT+PrZfPmOUkPe3+YSI9jGh2XqmwAT/w+LIPxr1j2WICmcdIBitq4YCLcteJwL2WxI1TAQSX0vI4ixjmH6kAuGT7UNxLiHHk4ZJiz25NjoCMWiIlT4bbzxu97V6OQkBYs9Q0I6CcCNrYrNU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755092325; c=relaxed/simple; bh=ivvFjuUqHzq8vh6cPGasq+coVZaTL9iXxS+y7Na9OoE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=iChBCqWKpefMfMag72OdHLtSWQSenoL6ecqXQdBr1+ohz4mEeGbUI8d5Z3LIwL/tp5E4ix9aZQq2+U4R//NtqL6exSfNYsCF2po5sx0yimOlcTyoTlyakd4C79cSa8B+cofzl5dZrHQ2blnsAs3bhraif955+6qTZXn4eJ2QYMs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZWJUZnn/; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ZWJUZnn/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4638DC4CEEB; Wed, 13 Aug 2025 13:38:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755092325; bh=ivvFjuUqHzq8vh6cPGasq+coVZaTL9iXxS+y7Na9OoE=; h=From:To:Cc:Subject:Date:From; b=ZWJUZnn/UdlayvDFuuUQ+rTqYYAql+NQP7TYz1+omiOFcC4vqd7qb9okw/uLBWxN5 wAqgEPJRmggdExVl9bdTCygsWD+z9VQ7D0aUHQ9NkAqpHnRRrPWPZtqj2o0OVV7iTH WxjlidS/DIEPytnJ+bUIwI2UqUWgNJCef7hsptyr+hGG2QzwqU8+PXm5tQ4prCITUo faniEBs3i//a9nMFwvvzcaG6rtVBoi02S9EvEMtmoVQLCO67zv1QxGGMjWGiqWDNup 1Tse6dGIOPPH8Ts6hHjeV3Q6+xT5EgzBA3IlqcfCnJHDVPcHZGWgWzYglmqy4vgjvV h/EzV0Ynor/VQ== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: syzbot+a9ed3d9132939852d0df@syzkaller.appspotmail.com, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , Hao Luo Subject: [PATCHv2 bpf] bpf: Check the helper function is valid in get_helper_proto Date: Wed, 13 Aug 2025 15:38:32 +0200 Message-ID: <20250813133832.755428-1-jolsa@kernel.org> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jiri Olsa syzbot reported an 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. Excluding tail_call helper from the check, because it is NULL by design and valid in all configs. [1] https://lore.kernel.org/bpf/68904050.050a0220.7f033.0001.GAE@google.com/ Reported-by: syzbot+a9ed3d9132939852d0df@syzkaller.appspotmail.com Suggested-by: Alexei Starovoitov Signed-off-by: Jiri Olsa --- v2 changes: - set bpf_tail_call_proto.func to -1 so we can skip the extra check [Andrii] 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 5d1650af899d..0f6e9a3d9960 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -3024,7 +3024,10 @@ 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 = (void *) 1, .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 c4f69a9e9af6..c89e2b1bc644 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11354,7 +11354,7 @@ 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, -- 2.50.1