From patchwork Tue Oct 8 15:21:17 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Amir Goldstein X-Patchwork-Id: 13826637 Received: from mail-ed1-f41.google.com (mail-ed1-f41.google.com [209.85.208.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8D7931E049E; Tue, 8 Oct 2024 15:21:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.41 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728400888; cv=none; b=sOkACajLMKce+IjdJ+aGtLktygHX3U6h5BOb7Vc0RVI3lFRB1SpYzP5HP/qn+tk0puLNBPIh05/gIRfLYSrEcyHz1LdgZJRCZX9Mur9GP0C/NhRpzlCUOhTdUSWPpXCF26+O/Nqwe9qwjm3X1PuDHuXp3KAB701lQWACGJJEDkg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728400888; c=relaxed/simple; bh=+lTbmtwfyb7AjlOxLrcSHxwkErVrBDtzdezP2YLKOJA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=nzyWjAM8K0ysVsWrVRBwTiYMT/vBmR3dAHTPvYG3BhS3PjMWdN8Ti86i8/QV5+b+o1qCH2Kr3T0gS117SK0jGBlORp/pJN8IjrCyjMOt6CJz7pMspmGEOSJBRcF8jmeSH75Fnag3hG1rL4sns5FVDcp8+fcV9e4mmvpjvA7Rwps= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=M8ol3jx9; arc=none smtp.client-ip=209.85.208.41 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="M8ol3jx9" Received: by mail-ed1-f41.google.com with SMTP id 4fb4d7f45d1cf-5c91a7141b8so232610a12.1; Tue, 08 Oct 2024 08:21:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1728400885; x=1729005685; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=7x/acSxCv7H+ppJ4OuFjM3Dd++gtKxDLriu5QQGsWoQ=; b=M8ol3jx9zOk2Z8Kk3Wz3OPckPXo5tddzGVPubrolkoIDkETwSepZh1WDEURWBuExiA ZDlWdo2IWjYZvK5uOurHW/zNLqCcAGpoWJTHOQTEcpeC5lRphBWYBuHvl7baMIAlQrm7 za2A24HtJ/8STx1NDFiDD9fzEPpkZqSmbtwHoT4mpPZay7dR7EyeiAZ+kQBpw690rKlo zcWwjzPfvjUEb+CriKc2i/7vUfCVxywC7202nTxbKx5+iNxt3wNqEMsrjZdQfXACKJNs +3bfoqXFZrCme/gUsCGRdvKnHCFbxIRgGwz1PEh7Oiv8P6OQJHwGhTqf7zR8AZg8+8X8 k6Xw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728400885; x=1729005685; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=7x/acSxCv7H+ppJ4OuFjM3Dd++gtKxDLriu5QQGsWoQ=; b=saLicXRZfInUPdOwOMNIqBlSTqmePfNqvqrRZ4KmUdSbpBxY/EyjS2CyR0BjL+t2fS X/tbmgipfY0oPOzTDTZoNRyrGcUpqjBoEJoMp877H0b7f7sgZ4YxA620aKfX5EFXma8a FR4hnSh1OZgFkqUY5iUUhqeVzCEivB0zo22cn7qFOgqdigbuxx4aAg8io3dnPi4qK0yZ B0teQt8yAurIXMnORocMm693sMVNBkYgm4OCjWfsJXtyt+vLiLNlXWbevU85VQRWKK0b PvzkouseValc8dpp4KT8b1jJg2exd8xS12MweNMZhx9wzesIBMpvxmxGC0iGkGwZpj32 5GVQ== X-Forwarded-Encrypted: i=1; AJvYcCU9IVmhMnPzOjVR+rTv2nPGc1krR9ryZtGjoHoaaK9kRrb8kEGJ3avCT+WeR4qqoB9b19KI60bFtwM3@vger.kernel.org, AJvYcCXT1+vwEb1fsdK+RUnoygNXQwJ8ZyV+uJxGs7+Xf2rOTXMfLWUIz/IldsHSCGFGwN3it11bUPHdx7vVliAU@vger.kernel.org X-Gm-Message-State: AOJu0Yz7awRdYhmpHVe+tn0JEl576e/6nl0Ai9dWnSrUDnquJH72bETj BUccPlWQRtBcg8uA10T87uxCSVvI/UY4IouXG8+UlnGcF8VpdnSjYxdUufKr X-Google-Smtp-Source: AGHT+IEKLxWVgobj8E72uSDt+XHtmNrE+X1Kl4tNw0NSo18GnMluZbKC1AjgMl/tBoXLvOko81/44A== X-Received: by 2002:a17:907:3e8e:b0:a99:65c6:7f22 with SMTP id a640c23a62f3a-a9965c68657mr303983566b.11.1728400884292; Tue, 08 Oct 2024 08:21:24 -0700 (PDT) Received: from amir-ThinkPad-T480.arnhem.chello.nl (92-109-99-123.cable.dynamic.v4.ziggo.nl. [92.109.99.123]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a99384f8258sm487910466b.16.2024.10.08.08.21.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Oct 2024 08:21:23 -0700 (PDT) From: Amir Goldstein To: Jeff Layton Cc: Christian Brauner , Jan Kara , Aleksa Sarai , Chuck Lever , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org Subject: [PATCH v3 2/3] fs: name_to_handle_at() support for "explicit connectable" file handles Date: Tue, 8 Oct 2024 17:21:17 +0200 Message-Id: <20241008152118.453724-3-amir73il@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241008152118.453724-1-amir73il@gmail.com> References: <20241008152118.453724-1-amir73il@gmail.com> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 nfsd encodes "connectable" file handles for the subtree_check feature, which can be resolved to an open file with a connected path. So far, userspace nfs server could not make use of this functionality. Introduce a new flag AT_HANDLE_CONNECTABLE to name_to_handle_at(2). When used, the encoded file handle is "explicitly connectable". The "explicitly connectable" file handle sets bits in the high 16bit of the handle_type field, so open_by_handle_at(2) will know that it needs to open a file with a connected path. old kernels will now recognize the handle_type with high bits set, so "explicitly connectable" file handles cannot be decoded by open_by_handle_at(2) on old kernels. The flag AT_HANDLE_CONNECTABLE is not allowed together with either AT_HANDLE_FID or AT_EMPTY_PATH. Signed-off-by: Amir Goldstein --- fs/fhandle.c | 48 ++++++++++++++++++++++++++++++++++---- include/linux/exportfs.h | 2 ++ include/uapi/linux/fcntl.h | 1 + 3 files changed, 46 insertions(+), 5 deletions(-) diff --git a/fs/fhandle.c b/fs/fhandle.c index c5792cf3c6e9..7b4c8945efcb 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -31,6 +31,14 @@ static long do_sys_name_to_handle(const struct path *path, if (!exportfs_can_encode_fh(path->dentry->d_sb->s_export_op, fh_flags)) return -EOPNOTSUPP; + /* + * A request to encode a connectable handle for a disconnected dentry + * is unexpected since AT_EMPTY_PATH is not allowed. + */ + if (fh_flags & EXPORT_FH_CONNECTABLE && + WARN_ON(path->dentry->d_flags & DCACHE_DISCONNECTED)) + return -EINVAL; + if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) return -EFAULT; @@ -45,7 +53,7 @@ static long do_sys_name_to_handle(const struct path *path, /* convert handle size to multiple of sizeof(u32) */ handle_dwords = f_handle.handle_bytes >> 2; - /* we ask for a non connectable maybe decodeable file handle */ + /* Encode a possibly decodeable/connectable file handle */ retval = exportfs_encode_fh(path->dentry, (struct fid *)handle->f_handle, &handle_dwords, fh_flags); @@ -67,8 +75,23 @@ static long do_sys_name_to_handle(const struct path *path, * non variable part of the file_handle */ handle_bytes = 0; - } else + } else { + /* + * When asked to encode a connectable file handle, encode this + * property in the file handle itself, so that we later know + * how to decode it. + * For sanity, also encode in the file handle if the encoded + * object is a directory and verify this during decode, because + * decoding directory file handles is quite different than + * decoding connectable non-directory file handles. + */ + if (fh_flags & EXPORT_FH_CONNECTABLE) { + handle->handle_type |= FILEID_IS_CONNECTABLE; + if (d_is_dir(path->dentry)) + fh_flags |= FILEID_IS_DIR; + } retval = 0; + } /* copy the mount id */ if (unique_mntid) { if (put_user(real_mount(path->mnt)->mnt_id_unique, @@ -109,15 +132,30 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, { struct path path; int lookup_flags; - int fh_flags; + int fh_flags = 0; int err; if (flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH | AT_HANDLE_FID | - AT_HANDLE_MNT_ID_UNIQUE)) + AT_HANDLE_MNT_ID_UNIQUE | AT_HANDLE_CONNECTABLE)) + return -EINVAL; + + /* + * AT_HANDLE_FID means there is no intention to decode file handle + * AT_HANDLE_CONNECTABLE means there is an intention to decode a + * connected fd (with known path), so these flags are conflicting. + * AT_EMPTY_PATH could be used along with a dfd that refers to a + * disconnected non-directory, which cannot be used to encode a + * connectable file handle, because its parent is unknown. + */ + if (flag & AT_HANDLE_CONNECTABLE && + flag & (AT_HANDLE_FID | AT_EMPTY_PATH)) return -EINVAL; + else if (flag & AT_HANDLE_FID) + fh_flags |= EXPORT_FH_FID; + else if (flag & AT_HANDLE_CONNECTABLE) + fh_flags |= EXPORT_FH_CONNECTABLE; lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; - fh_flags = (flag & AT_HANDLE_FID) ? EXPORT_FH_FID : 0; if (flag & AT_EMPTY_PATH) lookup_flags |= LOOKUP_EMPTY; err = user_path_at(dfd, name, lookup_flags, &path); diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index 76a3050b3593..230b0e1d669d 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -169,6 +169,8 @@ struct fid { #define FILEID_USER_FLAGS(type) ((type) & FILEID_USER_FLAGS_MASK) /* Flags supported in encoded handle_type that is exported to user */ +#define FILEID_IS_CONNECTABLE 0x10000 +#define FILEID_IS_DIR 0x40000 #define FILEID_VALID_USER_FLAGS (0) #define FILEID_USER_TYPE_IS_VALID(type) \ diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 87e2dec79fea..56ff2100e021 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -153,6 +153,7 @@ object identity and may not be usable with open_by_handle_at(2). */ #define AT_HANDLE_MNT_ID_UNIQUE 0x001 /* Return the u64 unique mount ID. */ +#define AT_HANDLE_CONNECTABLE 0x002 /* Request a connectable file handle */ #if defined(__KERNEL__) #define AT_GETATTR_NOSEC 0x80000000