From patchwork Tue Jul 25 13:45:04 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michael Tokarev X-Patchwork-Id: 1812551 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4R9JJR46T1z1yYC for ; Tue, 25 Jul 2023 23:48:07 +1000 (AEST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qOINU-0006vQ-Tn; Tue, 25 Jul 2023 09:47:05 -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 1qOINK-00060z-Dm; Tue, 25 Jul 2023 09:46:56 -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 1qOINH-0001bB-OW; Tue, 25 Jul 2023 09:46:54 -0400 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 06F36160FB; Tue, 25 Jul 2023 16:45:36 +0300 (MSK) Received: from tls.msk.ru (mjt.wg.tls.msk.ru [192.168.177.130]) by tsrv.corpit.ru (Postfix) with SMTP id AA87A194BE; Tue, 25 Jul 2023 16:45:33 +0300 (MSK) Received: (nullmailer pid 3370840 invoked by uid 1000); Tue, 25 Jul 2023 13:45:29 -0000 From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Helge Deller , "Markus F.X.J. Oberhumer" , Michael Tokarev Subject: [Stable-8.0.4 19/31] linux-user: Fix qemu brk() to not zero bytes on current page Date: Tue, 25 Jul 2023 16:45:04 +0300 Message-Id: <20230725134517.3370706-19-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+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Helge Deller The qemu brk() implementation is too aggressive and cleans remaining bytes on the current page above the last brk address. But some existing applications are buggy and read/write bytes above their current heap address. On a phyiscal machine this does not trigger a runtime error as long as the access happens on the same page. Additionally the Linux kernel allocates only full pages and does no zeroing on already allocated pages, even if the brk address is lowered. Fix qemu to behave the same way as the kernel does. Do not touch already allocated pages, and - when running with different page sizes of guest and host - zero out only those memory areas where the host page size is bigger than the guest page size. Signed-off-by: Helge Deller Tested-by: "Markus F.X.J. Oberhumer" Fixes: 86f04735ac ("linux-user: Fix brk() to release pages") Cc: qemu-stable@nongnu.org Buglink: https://github.com/upx/upx/issues/683 (cherry picked from commit 15ad98536ad9410fb32ddf1ff09389b677643faa) Signed-off-by: Michael Tokarev diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 57aaa87e30..450487af57 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -829,10 +829,8 @@ abi_long do_brk(abi_ulong brk_val) /* brk_val and old target_brk might be on the same page */ if (new_brk == TARGET_PAGE_ALIGN(target_brk)) { - if (brk_val > target_brk) { - /* empty remaining bytes in (possibly larger) host page */ - memset(g2h_untagged(target_brk), 0, new_host_brk_page - target_brk); - } + /* empty remaining bytes in (possibly larger) host page */ + memset(g2h_untagged(new_brk), 0, new_host_brk_page - new_brk); target_brk = brk_val; return target_brk; } @@ -840,7 +838,7 @@ abi_long do_brk(abi_ulong brk_val) /* Release heap if necesary */ if (new_brk < target_brk) { /* empty remaining bytes in (possibly larger) host page */ - memset(g2h_untagged(brk_val), 0, new_host_brk_page - brk_val); + memset(g2h_untagged(new_brk), 0, new_host_brk_page - new_brk); /* free unused host pages and set new brk_page */ target_munmap(new_host_brk_page, brk_page - new_host_brk_page); @@ -873,7 +871,7 @@ abi_long do_brk(abi_ulong brk_val) * come from the remaining part of the previous page: it may * contains garbage data due to a previous heap usage (grown * then shrunken). */ - memset(g2h_untagged(target_brk), 0, brk_page - target_brk); + memset(g2h_untagged(brk_page), 0, HOST_PAGE_ALIGN(brk_page) - brk_page); target_brk = brk_val; brk_page = new_host_brk_page;