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 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 86C90E7C6F9 for ; Sun, 1 Feb 2026 01:08:52 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vmLwl-0002yv-KJ; Sat, 31 Jan 2026 20:08:15 -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 1vmLwh-0002yi-EK for qemu-devel@nongnu.org; Sat, 31 Jan 2026 20:08:12 -0500 Received: from mail-wr1-x42c.google.com ([2a00:1450:4864:20::42c]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1vmLwe-000073-Oi for qemu-devel@nongnu.org; Sat, 31 Jan 2026 20:08:10 -0500 Received: by mail-wr1-x42c.google.com with SMTP id ffacd0b85a97d-4359a16a400so2866638f8f.1 for ; Sat, 31 Jan 2026 17:08:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1769908085; x=1770512885; darn=nongnu.org; h=content-transfer-encoding:mime-version:message-id:date:subject:to :from:from:to:cc:subject:date:message-id:reply-to; bh=MXvBNH349CruVNx0ankHtqUQYjA5qOdQSjNldxNhDmo=; b=lXggBoftBXCzwctio6oqvkPAbKPh36U7CI2jqlARSHblAm17ts9+JfHjUrEMmgTp3d Cs22RBnWMo17RwDDRgWG+ISa2Eow8Oxh19yoQnJDkw6keXkWAM9IxUbopRz1vwD8TxfD LltYAbfQ5s/QWsyPKC5zw1XxbxHy91rCTXBLySpWvGTh+fhC9id+gmRwQFcl3FBwCQZg Aq4EbC7mbqI7xV4oVMThwuvAbeQLPIlh6dENfdHqjlQJweFED1RDrYMHgWBf0mR0Ph8i rl4lG1TXdC5IhxiFF42ACUkQBbELjPHrtU3cuuFawmIqvGnvabFFZnieJOHPIAsbXq07 1Jug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1769908085; x=1770512885; h=content-transfer-encoding:mime-version:message-id:date:subject:to :from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=MXvBNH349CruVNx0ankHtqUQYjA5qOdQSjNldxNhDmo=; b=CHgdxMqqqR/KqHSOqxt61PIVtOp75MvaGwGvgZqxp6pQW6WB4slQzOo/OUFxzvD7/M k+6aeobobvUbBrz8TJkJJPVqIZm0BJp5Ube+00xQ/ePLycJBaIQKxABbByouFVb90DTc VqWdoAhF2Zas1jERGbG83j3/jCAZigST5xMDmUYFQ2Ywi1/uicAJPw1SyQ29C3SlYJZr +nUyQufigkYpQZt6Mm8YFSRXPU16PheKcnTQXq64btteUOpNmwIL9MG6cH1qCmFBRYmP E9gsIbobAUvp85C4ao2jMSX0ne7v8NejxSzJE3qznNmhU+49cZ00EoSkxWCXwpfuQsZP k+pA== X-Gm-Message-State: AOJu0YzIdMK+MqJZFPRjJ369nKqEbDe7/4w0XPi4C4NBWlIpASmL2G8P sWl9ICNZ10c1uH3tBWwoBmfAxkBXtz9bUrYHBVtZBzzwQDWOAJmRBgwLESi01Q== X-Gm-Gg: AZuq6aIEF9fEaQjFk/QgDAgB0nRjWq1TigJg/xn6ObAyghDYRSmhT5wMlqq6IylKPj9 oL8SaVMx/6ZkPZrjNkHBJ9mzsKszksjUDSCG0kuG5RJJkoGO4lTzy2lsb67R3GS8sp254OIi1yh AuHzMwhZeAI5sZhKLXWbNpI4yCXiaYDoV2ZGLUHWkBoPnl6LDWXWJK1keTXen1kLCtjH4FV1WNO ru5rhXIsEDe8tEosb5iYumBsTHLiFO0m/eQKvjGoe37JqyAgs9ILrYbPwxahZZGFVPanQrBHYCh F29TmsjSP0BRoq+IvCn81R1nV7ftgUjoARAPB5rwRa04gr/StUeevSUusJZq+vvkBcW8x/qmGeb 6wt2FLhVo4NTE9z5NjR3J0acjmuy4WQlFwMOjvfZg3KV9qz8WZzgdXPu+aHPkHl8qc9NZjbfXZb MU71GpSKm/2+8NI9aGZwcVFvgBP6UBNfLA+fAv2yU= X-Received: by 2002:a5d:5f54:0:b0:430:fd0f:2910 with SMTP id ffacd0b85a97d-435f3a92801mr10979253f8f.26.1769908084372; Sat, 31 Jan 2026 17:08:04 -0800 (PST) Received: from localhost.localdomain ([92.180.8.65]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435e10ed952sm33922358f8f.10.2026.01.31.17.08.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 31 Jan 2026 17:08:04 -0800 (PST) From: Razvan Ghiorghe To: qemu-devel@nongnu.org, laurent@vivier.eu, razvanghiorghe16@gmail.com Subject: [PATCH v2] linux-user: Fix mremap() with old_size == 0 Date: Sun, 1 Feb 2026 03:03:43 +0200 Message-ID: <20260201010436.5735-1-razvanghiorghe16@gmail.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::42c; envelope-from=razvanghiorghe16@gmail.com; helo=mail-wr1-x42c.google.com X-Spam_score_int: -7 X-Spam_score: -0.8 X-Spam_bar: / X-Spam_report: (-0.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FORGED_GMAIL_RCVD=1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 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 == 0 behaviour. This patch adds proper handling for old_size == 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 beeing valid and sharing the same physical memory frames. Tested with the reproducer from the issue on qemu-riscv64. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/3105 Signed-off-by: Razvan Ghiorghe --- linux-user/mmap.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 4bcfaf7894..b1a84eb60a 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -1117,6 +1117,38 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, errno = EINVAL; return -1; } + + if (!old_size) { + if (!(flags & MREMAP_MAYMOVE)) { + errno = EINVAL; + return -1; + } + mmap_lock(); + if (flags & MREMAP_FIXED) { + host_addr = mremap(g2h_untagged(old_addr), old_size, new_size, + flags, g2h_untagged(new_addr)); + } else { + host_addr = mremap(g2h_untagged(old_addr), old_size, new_size, + flags); + } + + if (host_addr == MAP_FAILED) { + mmap_unlock(); + return -1; + } + new_addr = h2g(host_addr); + prot = 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 = EFAULT; return -1; -- 2.43.0