From patchwork Tue Oct 27 13:55:27 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 307456 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 01BA3C5DF9D for ; Tue, 27 Oct 2020 15:56:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9C00F20829 for ; Tue, 27 Oct 2020 15:56:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603814191; bh=MVcA8RairfrcRn+2/dlyy4yyOnFWH1hl4AupGXpwJkg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=XHHW5Ij0MeXJbp7LONM0SZs/9XtxfDsHmM9h2jyrNrr+Dm7gGLlzy/FHDFepnMQYm tcCWvJfj0e/WUwwh/hxUZaOcnXXg01ig1/zMT48L7BaInMkQ/DX9Yw+rJykb90XYUR ewLnfKX7Q1USroyIpE0deT9dEEA0tbfVkTVGP+yI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1802518AbgJ0Ptz (ORCPT ); Tue, 27 Oct 2020 11:49:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:53176 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757267AbgJ0PQZ (ORCPT ); Tue, 27 Oct 2020 11:16:25 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 669A820728; Tue, 27 Oct 2020 15:16:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603811785; bh=MVcA8RairfrcRn+2/dlyy4yyOnFWH1hl4AupGXpwJkg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ex4iFd2ViH8kbBuJa8uAFX/8KhvzbrF8w8H6ppQv9uCJauUBsebJJYOhOXR4uqosN rb/r9NTN6IUyBbRm6DGAUNNLbZiwlUrq0YqlwPhIAQ0RJRGObsl4a26LnKMjRiZVLB Db1LLQiHa79R9+QPkE1D1ODwOk1S3+Q5JLZSr9kw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexei Starovoitov , Maciej Fijalkowski , Sasha Levin Subject: [PATCH 5.8 584/633] bpf: Limit callers stack depth 256 for subprogs with tailcalls Date: Tue, 27 Oct 2020 14:55:27 +0100 Message-Id: <20201027135550.203241920@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135522.655719020@linuxfoundation.org> References: <20201027135522.655719020@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Maciej Fijalkowski [ Upstream commit 7f6e4312e15a5c370e84eaa685879b6bdcc717e4 ] Protect against potential stack overflow that might happen when bpf2bpf calls get combined with tailcalls. Limit the caller's stack depth for such case down to 256 so that the worst case scenario would result in 8k stack size (32 which is tailcall limit * 256 = 8k). Suggested-by: Alexei Starovoitov Signed-off-by: Maciej Fijalkowski Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 30 insertions(+) diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index ca08db4ffb5f7..ce3f5231aa698 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -358,6 +358,7 @@ struct bpf_subprog_info { u32 start; /* insn idx of function entry point */ u32 linfo_idx; /* The idx to the main_prog->aux->linfo */ u16 stack_depth; /* max. stack depth used by this function */ + bool has_tail_call; }; /* single container for all structs diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c953dfbbaa6a9..12eb9e47d101c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1470,6 +1470,10 @@ static int check_subprogs(struct bpf_verifier_env *env) for (i = 0; i < insn_cnt; i++) { u8 code = insn[i].code; + if (code == (BPF_JMP | BPF_CALL) && + insn[i].imm == BPF_FUNC_tail_call && + insn[i].src_reg != BPF_PSEUDO_CALL) + subprog[cur_subprog].has_tail_call = true; if (BPF_CLASS(code) != BPF_JMP && BPF_CLASS(code) != BPF_JMP32) goto next; if (BPF_OP(code) == BPF_EXIT || BPF_OP(code) == BPF_CALL) @@ -2951,6 +2955,31 @@ static int check_max_stack_depth(struct bpf_verifier_env *env) int ret_prog[MAX_CALL_FRAMES]; process_func: + /* protect against potential stack overflow that might happen when + * bpf2bpf calls get combined with tailcalls. Limit the caller's stack + * depth for such case down to 256 so that the worst case scenario + * would result in 8k stack size (32 which is tailcall limit * 256 = + * 8k). + * + * To get the idea what might happen, see an example: + * func1 -> sub rsp, 128 + * subfunc1 -> sub rsp, 256 + * tailcall1 -> add rsp, 256 + * func2 -> sub rsp, 192 (total stack size = 128 + 192 = 320) + * subfunc2 -> sub rsp, 64 + * subfunc22 -> sub rsp, 128 + * tailcall2 -> add rsp, 128 + * func3 -> sub rsp, 32 (total stack size 128 + 192 + 64 + 32 = 416) + * + * tailcall will unwind the current stack frame but it will not get rid + * of caller's stack as shown on the example above. + */ + if (idx && subprog[idx].has_tail_call && depth >= 256) { + verbose(env, + "tail_calls are not allowed when call stack of previous frames is %d bytes. Too large\n", + depth); + return -EACCES; + } /* round up to 32-bytes, since this is granularity * of interpreter stack size */