From nobody Tue Apr 7 16:14:45 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; dkim=pass; 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; dmarc=pass(p=quarantine dis=none) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; t=1773346412; cv=none; d=zohomail.com; s=zohoarc; b=AB7A1pAZgln7BtICHQjDnxzBSzzaA4touuf3+hEKemCSiEuMRZzx0G2KnGMm2z8bWDLvSXRtvdsJ8yIGELiG1PpCxsKpF+1t94DVcUO3ffjbZN6tuz4KRldpNNVreSygzrs2ul4c19vikqngv9RT3L88NDHeSuxIeSjmOKuXnBY= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1773346412; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=fpzPZvf4lGg/YV04gcwA1Ds3uYOT4KMbk4tjGAtyFro=; b=SGL8WjK4eTPcZgTwqp+dUwVeWukGWLGTA+fhCeXMUIlcZfX+/op4vV8V1U04+yPoRzlv1tZgvDdnoRS53U/1o9MMpvxjT9atYB6+ijxtCm1HQj9z6WBxZZGtUzjmKqwMEAqIzguwgf2T3OMzas8UEw6+q1yLq3+J6GZfn2GbxrA= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; 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; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 177334641205815.013016072990922; Thu, 12 Mar 2026 13:13:32 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1w0mOq-0004fk-Bk; Thu, 12 Mar 2026 16:12:52 -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 1w0mOm-0004dU-LQ for qemu-devel@nongnu.org; Thu, 12 Mar 2026 16:12:48 -0400 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1w0mOk-0006Yl-Po for qemu-devel@nongnu.org; Thu, 12 Mar 2026 16:12:48 -0400 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 0605E42A5C; Thu, 12 Mar 2026 20:12:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 04754C4CEF7; Thu, 12 Mar 2026 20:12:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773346364; bh=IoVriGbsFQSGgBcb5APt3WGdcnQHDFn1QXcp46ncTuE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q9fLDkMcuX6XPLFxOOMYKrUoPgUHnIoWmpCArRmJDHaPDAi9581FqFj3im3mfpcv/ GHVc6bY1tdMxXLmNvTGi8bvyhRCJ4/r0ai/9qMQTFbhF8BJnVcwSlSPscbPx0tlzOW XoL56+nQm+2GRckRbekalF3SlpmmNwgHKpPqZnHQx+LNQuBj8k5ckk1DotpxqzUgfu 8L6P1cpUiYPfOblZuFY23Tv0FIIcXzO2xSCrFVMStJ/Ux9iFzahs5YQNMxwHgU7Sza 4Y6S2QUUIYqGgus5fUrPoEj8IGTnCsXbisOwW7waHlCc+fLH8x3xCT30xc4SpZvB4y y4hpfNYhCOFCg== From: Helge Deller To: qemu-devel@nongnu.org Cc: Laurent Vivier , Helge Deller Subject: [PATCH 2/2] linux-user: fix mremap with old_size=0 for shared mappings Date: Thu, 12 Mar 2026 21:12:39 +0100 Message-ID: <20260312201239.2976-3-deller@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260312201239.2976-1-deller@kernel.org> References: <20260312201239.2976-1-deller@kernel.org> 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=2600:3c0a:e001:78e:0:1991:8:25; envelope-from=deller@kernel.org; helo=sea.source.kernel.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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-ZohoMail-DKIM: pass (identity @kernel.org) X-ZM-MESSAGEID: 1773346413302158500 Content-Type: text/plain; charset="utf-8" From: Razvan Ghiorghe When old_size is zero and old_address refers to a shareable mapping, mremap() should create a new mapping of the same pages according to the mremap(2) man page. The MREMAP_MAYMOVE flag must be specified in this case. Previously, QEMU's target_mremap() rejected this valid case with EFAULT during the initial validation, before checking for the special old_size =3D=3D 0 behaviour. This patch adds proper handling for old_size =3D=3D 0: - Validates that MREMAP_MAYMOVE flag is set (required by man spec) - Passes the call through to the host mremap() - Creates a new mapping without invalidating the original, with both being valid and sharing the same physical memory frames. - Ensures the new mapping address falls within the valid guest address region before returning it to the guest. Tested with the reproducer from the issue on qemu-riscv64, qemu-hppa, and qemu-aarch64. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3105 Signed-off-by: Razvan Ghiorghe Tested-by: Helge Deller Reviewed-by: Helge Deller Signed-off-by: Helge Deller --- linux-user/mmap.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 76978a56a8..b635b6a21c 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -1120,6 +1120,58 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong= old_size, errno =3D EINVAL; return -1; } + + if (!old_size) { + if (!(flags & MREMAP_MAYMOVE)) { + errno =3D EINVAL; + return -1; + } + mmap_lock(); + if (flags & MREMAP_FIXED) { + host_addr =3D mremap(g2h_untagged(old_addr), old_size, new_siz= e, + flags, g2h_untagged(new_addr)); + } else { + /* + * We ensure that the new mapping stands in the + * region of guest mappable addresses. + */ + abi_ulong mmap_start; + + mmap_start =3D mmap_find_vma(0, new_size, TARGET_PAGE_SIZE); + + if (mmap_start =3D=3D -1) { + errno =3D ENOMEM; + mmap_unlock(); + return -1; + } + + host_addr =3D mremap(g2h_untagged(old_addr), old_size, new_siz= e, + flags | MREMAP_FIXED, g2h_untagged(mmap_start= )); + + new_addr =3D mmap_start; + } + + if (host_addr =3D=3D MAP_FAILED) { + mmap_unlock(); + return -1; + } + + if (flags & MREMAP_FIXED) { + new_addr =3D h2g(host_addr); + } + + prot =3D page_get_flags(old_addr); + /* + * For old_size zero, there is nothing to clear at old_addr. + * Only set the flags for the new mapping. They both are valid. + */ + page_set_flags(new_addr, new_addr + new_size - 1, + prot | PAGE_VALID, PAGE_VALID); + shm_region_rm_complete(new_addr, new_addr + new_size - 1); + mmap_unlock(); + return new_addr; + } + if (!guest_range_valid_untagged(old_addr, old_size)) { errno =3D EFAULT; return -1; --=20 2.53.0