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Thu, 20 Nov 2025 05:01:41 -0800 (PST) Received: from [192.168.43.207] ([188.113.193.112]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42cb7fd8e54sm5282754f8f.40.2025.11.20.05.01.39 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Nov 2025 05:01:40 -0800 (PST) Message-ID: <5e07267f-b990-47fc-ade7-934209ea942f@gmail.com> Date: Thu, 20 Nov 2025 18:01:36 +0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: qemu-devel@nongnu.org From: Andrey Erokhin Subject: [PATCH] hw/9pfs: Follow native symlinks when security-model=mapped Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=2a00:1450:4864:20::429; envelope-from=language.lawyer@gmail.com; helo=mail-wr1-x429.google.com 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Thu, 20 Nov 2025 09:27:05 -0500 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 A directory mounted via virtfs with security-model=mapped[-xattr|-file] can contain "native" symlinks This can happen e.g. when booting from a rootfs directory tree (usually with writable overlay set up on the host side) Currently, with security-model=mapped, QEMU expects that all host "symlinks" are in "mapped" format, i.e. are files containing the linked path, so it tries to open with O_NOFOLLOW and fails with ELOOP in case of a native symlink This patch gives such cases a second chance: trying to open as a native symlink, by reusing security-model=[none|passthrough] else if branch QEMU issues: https://gitlab.com/qemu-project/qemu/-/issues/173 (from https://bugs.launchpad.net/qemu/+bug/1831354) https://gitlab.com/qemu-project/qemu/-/issues/3088 (dup of the first one) Signed-off-by: Andrey Erokhin diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 31e216227c..b4f8be2c81 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -468,12 +468,14 @@ static ssize_t local_readlink(FsContext *fs_ctx, V9fsPath *fs_path, fd = local_open_nofollow(fs_ctx, fs_path->data, O_RDONLY, 0); if (fd == -1) { + if (errno == ELOOP) goto native_symlink; return -1; } tsize = RETRY_ON_EINTR(read(fd, (void *)buf, bufsz)); close_preserve_errno(fd); } else if ((fs_ctx->export_flags & V9FS_SM_PASSTHROUGH) || (fs_ctx->export_flags & V9FS_SM_NONE)) { +native_symlink:; char *dirpath = g_path_get_dirname(fs_path->data); char *name = g_path_get_basename(fs_path->data); int dirfd;