From patchwork Tue Oct 27 13:55:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 289908 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 30FE4C55178 for ; Tue, 27 Oct 2020 14:54:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5FB5222EA for ; Tue, 27 Oct 2020 14:53:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603810439; bh=qBf58oDai6bWC91U46c4PuXGWtEl4hhIe0JUylRGiZk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=jPe97L5jUUkL1Easv560Otz4SCYVtHtkiAx5jiXMyX5LFpbzQ7+TYWI9qB2pR4nb0 ycLYlBFDKrarRCjueJ1TCbhhOjii0CCvGSPoVXLCjGNI9xOxPDxFj1aPUYGyp7qTFY 5XUT7OLwswLS7djZ8YWZ/K/opcH2ONLCQkFxF4hw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752347AbgJ0Ox6 (ORCPT ); Tue, 27 Oct 2020 10:53:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:45270 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763873AbgJ0OpW (ORCPT ); Tue, 27 Oct 2020 10:45:22 -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 9A145206E5; Tue, 27 Oct 2020 14:45:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603809921; bh=qBf58oDai6bWC91U46c4PuXGWtEl4hhIe0JUylRGiZk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=adsTu3m9GhO0aefvYKNwgIUjOjL+2TbV0Xemnl/q0oyWxc1j1UAq3A7p1EHUmx+H0 Vl7VtRsHww3inmkYTLpLMr/lrRF3fy8/f989kIj1NkE88cpoV0Pr1DZDFwY2BPH4Tn 90sgrXXscbrrGgzVD30ZZg3TniZrasvVNjoqR5v0= 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 5.4 366/408] bpf: Limit callers stack depth 256 for subprogs with tailcalls Date: Tue, 27 Oct 2020 14:55:04 +0100 Message-Id: <20201027135512.002021094@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135455.027547757@linuxfoundation.org> References: <20201027135455.027547757@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 26a6d58ca78cc..81c7ea83e8079 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -342,6 +342,7 @@ 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 ae27dd77a73cb..507474f79195f 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1160,6 +1160,10 @@ 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) @@ -2612,6 +2616,31 @@ 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 */