From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A109EC77B7E for ; Sun, 28 May 2023 19:46:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231307AbjE1Tqs (ORCPT ); Sun, 28 May 2023 15:46:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33096 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231309AbjE1Tqs (ORCPT ); Sun, 28 May 2023 15:46:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0CF613D for ; Sun, 28 May 2023 12:46:33 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 101A961F7B for ; Sun, 28 May 2023 19:46:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 093C4C433D2; Sun, 28 May 2023 19:46:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1685303192; bh=d/x17/jd7iQLxKtO5qTgvwAuERRzsguRisOTzBKf9x4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oRrTVzksUhzO2SQN8sYrz7WJFt01Jic4ZP8efm8/fYgJMExi4+4ImkZl7FMfdjgYI SmPBiM1o+wutpv4Rh7LF3W1XkPc/Kf7fYS/T7uiyohbQ1aQqe2wcrpsxejYWgL44p4 /etnAAqVBwn8iLs6ulENp07Esu4ZFLuh87rX0AMk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alexei Starovoitov , Daniel Borkmann , John Fastabend , Krzesimir Nowak , Andrey Ignatov , Yonghong Song , Will Deacon Subject: [PATCH 5.10 192/211] bpf: Fix mask generation for 32-bit narrow loads of 64-bit fields Date: Sun, 28 May 2023 20:11:53 +0100 Message-Id: <20230528190848.270380591@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230528190843.514829708@linuxfoundation.org> References: <20230528190843.514829708@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Will Deacon commit 0613d8ca9ab382caabe9ed2dceb429e9781e443f upstream. A narrow load from a 64-bit context field results in a 64-bit load followed potentially by a 64-bit right-shift and then a bitwise AND operation to extract the relevant data. In the case of a 32-bit access, an immediate mask of 0xffffffff is used to construct a 64-bit BPP_AND operation which then sign-extends the mask value and effectively acts as a glorified no-op. For example: 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0) results in the following code generation for a 64-bit field: ldr x7, [x7] // 64-bit load mov x10, #0xffffffffffffffff and x7, x7, x10 Fix the mask generation so that narrow loads always perform a 32-bit AND operation: ldr x7, [x7] // 64-bit load mov w10, #0xffffffff and w7, w7, w10 Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: John Fastabend Cc: Krzesimir Nowak Cc: Andrey Ignatov Acked-by: Yonghong Song Fixes: 31fd85816dbe ("bpf: permits narrower load from bpf program context fields") Signed-off-by: Will Deacon Link: https://lore.kernel.org/r/20230518102528.1341-1-will@kernel.org Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/verifier.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11146,7 +11146,7 @@ static int convert_ctx_accesses(struct b insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH, insn->dst_reg, shift); - insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg, + insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg, (1ULL << size * 8) - 1); } }