From patchwork Fri Sep 6 06:53:52 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 13793446 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A7BB9CE7AE0 for ; Fri, 6 Sep 2024 06:57:36 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1smStN-0004D3-Mn; Fri, 06 Sep 2024 02:56:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1smStL-0003v4-No; Fri, 06 Sep 2024 02:56:23 -0400 Received: from isrv.corpit.ru ([86.62.121.231]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1smStK-0003ND-1e; Fri, 06 Sep 2024 02:56:23 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 200868C24B; Fri, 6 Sep 2024 09:53:13 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id DDAA2133403; Fri, 6 Sep 2024 09:54:30 +0300 (MSK) Received: (nullmailer pid 43484 invoked by uid 1000); Fri, 06 Sep 2024 06:54:30 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Peter Maydell , Richard Henderson , Michael Tokarev Subject: [Stable-8.2.7 22/53] target/arm: Avoid shifts by -1 in tszimm_shr() and tszimm_shl() Date: Fri, 6 Sep 2024 09:53:52 +0300 Message-Id: <20240906065429.42415-22-mjt@tls.msk.ru> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Received-SPF: pass client-ip=86.62.121.231; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -68 X-Spam_score: -6.9 X-Spam_bar: ------ X-Spam_report: (-6.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Peter Maydell The function tszimm_esz() returns a shift amount, or possibly -1 in certain cases that correspond to unallocated encodings in the instruction set. We catch these later in the trans_ functions (generally with an "a-esz < 0" check), but before we do the decodetree-generated code will also call tszimm_shr() or tszimm_sl(), which will use the tszimm_esz() return value as a shift count without checking that it is not negative, which is undefined behaviour. Avoid the UB by checking the return value in tszimm_shr() and tszimm_shl(). Cc: qemu-stable@nongnu.org Resolves: Coverity CID 1547617, 1547694 Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Message-id: 20240722172957.1041231-4-peter.maydell@linaro.org (cherry picked from commit 76916dfa89e8900639c1055c07a295c06628a0bc) Signed-off-by: Michael Tokarev diff --git a/target/arm/tcg/translate-sve.c b/target/arm/tcg/translate-sve.c index ada05aa530..466a19c25a 100644 --- a/target/arm/tcg/translate-sve.c +++ b/target/arm/tcg/translate-sve.c @@ -50,13 +50,27 @@ static int tszimm_esz(DisasContext *s, int x) static int tszimm_shr(DisasContext *s, int x) { - return (16 << tszimm_esz(s, x)) - x; + /* + * We won't use the tszimm_shr() value if tszimm_esz() returns -1 (the + * trans function will check for esz < 0), so we can return any + * value we like from here in that case as long as we avoid UB. + */ + int esz = tszimm_esz(s, x); + if (esz < 0) { + return esz; + } + return (16 << esz) - x; } /* See e.g. LSL (immediate, predicated). */ static int tszimm_shl(DisasContext *s, int x) { - return x - (8 << tszimm_esz(s, x)); + /* As with tszimm_shr(), value will be unused if esz < 0 */ + int esz = tszimm_esz(s, x); + if (esz < 0) { + return esz; + } + return x - (8 << esz); } /* The SH bit is in bit 8. Extract the low 8 and shift. */