From patchwork Mon Apr 19 13:06:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 425214 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, 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 6A773C433B4 for ; Mon, 19 Apr 2021 13:15:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49BE0613C9 for ; Mon, 19 Apr 2021 13:15:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240450AbhDSNQP (ORCPT ); Mon, 19 Apr 2021 09:16:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:47170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240459AbhDSNOO (ORCPT ); Mon, 19 Apr 2021 09:14:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id ACDF161360; Mon, 19 Apr 2021 13:12:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1618837962; bh=wsJbThG5akXZYP6Eh4T3CgwSyfAvBybPK5swGOWTeNw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WgyS7UcjbocOXh28tvzgDJG0fhrmkV/OyK/Ly+BC4Df0jb3mxZ93F7FcrNADyTLCn Cdc1yMgv7ggpAmbgRUTOqdH4YYCZoj5L62pvbcgEv0Esj1tk/wvuXC96cHmH54DzXF nXLgb7XB8eBGFK9ki7+eevtiHUyiV6P9gbydrFLI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Daniel Borkmann , John Fastabend , Alexei Starovoitov , Sasha Levin Subject: [PATCH 5.11 117/122] bpf: Ensure off_reg has no mixed signed bounds for all types Date: Mon, 19 Apr 2021 15:06:37 +0200 Message-Id: <20210419130534.143126272@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210419130530.166331793@linuxfoundation.org> References: <20210419130530.166331793@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Daniel Borkmann [ Upstream commit 24c109bb1537c12c02aeed2d51a347b4d6a9b76e ] The mixed signed bounds check really belongs into retrieve_ptr_limit() instead of outside of it in adjust_ptr_min_max_vals(). The reason is that this check is not tied to PTR_TO_MAP_VALUE only, but to all pointer types that we handle in retrieve_ptr_limit() and given errors from the latter propagate back to adjust_ptr_min_max_vals() and lead to rejection of the program, it's a better place to reside to avoid anything slipping through for future types. The reason why we must reject such off_reg is that we otherwise would not be able to derive a mask, see details in 9d7eceede769 ("bpf: restrict unknown scalars of mixed signed bounds for unprivileged"). Signed-off-by: Daniel Borkmann Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b654174619e5..fe473e565092 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -5385,12 +5385,18 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env) } static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg, - u32 *ptr_limit, u8 opcode, bool off_is_neg) + const struct bpf_reg_state *off_reg, + u32 *ptr_limit, u8 opcode) { + bool off_is_neg = off_reg->smin_value < 0; bool mask_to_left = (opcode == BPF_ADD && off_is_neg) || (opcode == BPF_SUB && !off_is_neg); u32 off, max; + if (!tnum_is_const(off_reg->var_off) && + (off_reg->smin_value < 0) != (off_reg->smax_value < 0)) + return -EACCES; + switch (ptr_reg->type) { case PTR_TO_STACK: /* Offset 0 is out-of-bounds, but acceptable start for the @@ -5483,7 +5489,7 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, alu_state |= ptr_is_dst_reg ? BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST; - err = retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg); + err = retrieve_ptr_limit(ptr_reg, off_reg, &alu_limit, opcode); if (err < 0) return err; @@ -5528,8 +5534,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value; u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value, umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value; - u32 dst = insn->dst_reg, src = insn->src_reg; u8 opcode = BPF_OP(insn->code); + u32 dst = insn->dst_reg; int ret; dst_reg = ®s[dst]; @@ -5577,13 +5583,6 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, verbose(env, "R%d pointer arithmetic on %s prohibited\n", dst, reg_type_str[ptr_reg->type]); return -EACCES; - case PTR_TO_MAP_VALUE: - if (!env->env->bypass_spec_v1 && !known && (smin_val < 0) != (smax_val < 0)) { - verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n", - off_reg == dst_reg ? dst : src); - return -EACCES; - } - fallthrough; default: break; }