From nobody Tue Feb 10 11:15:21 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1770061754760637.1830431975557; Mon, 2 Feb 2026 11:49:14 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vmzuw-00045q-6t; Mon, 02 Feb 2026 14:49:02 -0500 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 1vmzut-0003tF-JM; Mon, 02 Feb 2026 14:48:59 -0500 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vmzus-0003TU-1M; Mon, 02 Feb 2026 14:48:59 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id B3D761850AF; Mon, 02 Feb 2026 22:46:04 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 6704935B291; Mon, 02 Feb 2026 22:46:46 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Matthew Lugg , Richard Henderson , Michael Tokarev Subject: [Stable-10.0.8 29/69] linux-user: fix reserved_va page leak in do_munmap Date: Mon, 2 Feb 2026 22:45:52 +0300 Message-ID: <20260202194638.939438-29-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1770061757317154100 Content-Type: text/plain; charset="utf-8" From: Matthew Lugg The old logic had an off-by-one bug. For instance, assuming 4k pages on host and guest, if 'len' is '4097' (indicating to unmap 2 pages), then 'last =3D start + 4096', so 'real_last =3D start + 4095', so ultimately 'real_len =3D 4096'. I do not believe this could cause any observable bugs in guests, because `target_munmap` page-aligns the length it passes in. However, calls to this function in `target_mremap` do not page-align the length, so those calls could "drop" pages, leading to a part of the reserved region becoming unmapped. At worst, a host allocation could get mapped into that hole, then clobbered by a new guest mapping. Signed-off-by: Matthew Lugg Reviewed-by: Richard Henderson Signed-off-by: Richard Henderson Message-ID: <20251117170954.31451-4-mlugg@mlugg.co.uk> (cherry picked from commit 81ceab30492ed251addae8539f7b69a069b0f984) Signed-off-by: Michael Tokarev diff --git a/linux-user/mmap.c b/linux-user/mmap.c index dc28470054..568538d833 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -1027,9 +1027,9 @@ static int mmap_reserve_or_unmap(abi_ulong start, abi= _ulong len) void *host_start; int prot; =20 - last =3D start + len - 1; + last =3D ROUND_UP(start + len, TARGET_PAGE_SIZE) - 1; real_start =3D start & -host_page_size; - real_last =3D ROUND_UP(last, host_page_size) - 1; + real_last =3D ROUND_UP(last + 1, host_page_size) - 1; =20 /* * If guest pages remain on the first or last host pages, --=20 2.47.3