From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794590031; b=vrE+5Qu1TxvHqGErA6Zc+Z0degFzQfusP5l3DYpTfQ7bHGmTUcR52bhnhqqLRjX3c4nF j3ZmtwWQv2Z0LAD4NJUun94y2z4rfdKk5z6bh/lX8xV7Iroh7RRIXctqBlGX7TmGW8eRn hML4NBUQfV6ij5rIqDaq4M3DtKNr8fgSrOSDPM650gJzw0hOQNb+rla3hHeLOioVB8bNs x6gvxB1GO2sUd5A0pAhSLUxDGoZKgKd2buXMQhviX9uae/MQsolmKnwdSnMkFdSwFOFbc SgpclO7qSOQQqlfbkAmZeiKYaSnMfftBkfYuhNvOznaaIUNrjmfDO1nW2HgGBN6TOfw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794590031; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=44xsyDZpcvRPcoG6a5XzFPXjnacUo/NcpXdynDYNAgU=; b=uje5e3GkXJWME8bz2K96eNJJZQXl3szG4ARA9m2AAec70i7GYVxzAQjF4sk1DyYOyBF/ l5fdq09hS3SGx51EZe48etNaHkegp1qgWMuJM9unEK9v/nYVi54XLGBgboRU3s1GaxQKK uZ/2eLjjq9BB9QjPm4QNy2VvxCZbx4SnnxPkjrjA6iS5BuwlT6u4m7l9iLWNnmwQcGqYX fAqlY9c+5+vXpSJSaq5esjabF+6ELI1R20l1/0AJywBLl+SznytTy1B9hfs0X2kqVQMz7 8Xo8vo3hBcKxO4Wnq+iv7LRsfjInFu60RsK1d+GA/FFnCutgU9tpJLaIAqbWJOhRy5w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=lNFnKD7k; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 426B360A3826; Fri, 13 Nov 2026 17:13:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=lNFnKD7k Received: by smtp.kernel.org (Postfix) with ESMTPSA id E18AA1F000C5; Fri, 13 Nov 2026 17:13:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794590031; bh=44xsyDZpcvRPcoG6a5XzFPXjnacUo/NcpXdynDYNAgU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=lNFnKD7k6cgAT0erQDGZi5d6TqIgu9SBlmZhxoaNtVVzUqi0mf7tLzAvu48OURpBK qPGy3Op4tA8gbBQQgXkxdSgVjmZwqzOLyMnAlti2dOzVotbU6dtZUthbNXFMC9/O2f 8X4Fs5eXCs9FObWPpTkFxE5xiDnIxf6O2ubDPJXM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrey Albershteyn , Eric Biggers , Sasha Levin Subject: [PATCH 6.18 069/686] fsverity: Explicitly require FMODE_READ to retrieve hashes Date: Fri, 13 Nov 2026 10:43:22 -0500 Message-ID: <20261113153823.256167534@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153820.902362109@linuxfoundation.org> References: <20261113153820.902362109@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 1acb4fd2d011c4bd6cc961095ae17361c71ff61a upstream. The comment in fsverity_ioctl_read_metadata(), which justifies not checking for FMODE_READ, doesn't consider that the nonstandard access mode 3 (ioctl-only) exists. Opening an ioctl-only fd generally requires read (and write) permission. However, there are gaps with certain LSMs: an ioctl-only fd requests read (and write) permission via security_inode_permission, but not security_file_open. With certain LSMs relying on the latter, such as Landlock and AppArmor, an ioctl-only fd can be opened without the LSM granting read (and write) permission. Since FS_IOC_READ_VERITY_METADATA returns hashes of file contents blocks, it should require read permission. This also applies to FS_IOC_MEASURE_VERITY, which returns a hash for the whole file. Meanwhile, ioctl-only fds are a rarely-used feature, not known to be used with either ioctl. Therefore, just disallow these ioctls on ioctl-only file descriptors, similar to what was already done with FS_IOC_ENABLE_VERITY. More specifically, explicitly check for FMODE_READ. This also covers write-only fds to non-verity files which otherwise would have failed with ENODATA. This change in error code for write-only fds should be fine too, as these ioctls cannot be usefully used with write-only fds anyway, but it's worth noting as another technicality. Fixes: 4dd893d832cf ("fs-verity: implement FS_IOC_MEASURE_VERITY ioctl") Fixes: e17fe6579de0 ("fs-verity: add FS_IOC_READ_VERITY_METADATA ioctl") Cc: stable@vger.kernel.org Reviewed-by: Andrey Albershteyn Link: https://patch.msgid.link/20261022211522.1489943-1-ebiggers@kernel.org Signed-off-by: Eric Biggers Signed-off-by: Sasha Levin --- Documentation/filesystems/fsverity.rst | 3 +++ fs/verity/measure.c | 10 ++++++++++ fs/verity/read_metadata.c | 14 ++++++++++---- 3 files changed, 23 insertions(+), 4 deletions(-) diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 412cf11e32985..fd17bbf5795c9 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -170,6 +170,7 @@ fatal signal), no changes are made to the file. FS_IOC_ENABLE_VERITY can fail with the following errors: - ``EACCES``: the process does not have write access to the file +- ``EBADF``: the file descriptor is not open for reading - ``EBADMSG``: the builtin signature is malformed - ``EBUSY``: this ioctl is already running on the file - ``EEXIST``: the file already has verity enabled @@ -232,6 +233,7 @@ regardless of the size of the file. FS_IOC_MEASURE_VERITY can fail with the following errors: +- ``EBADF``: the file descriptor is not open for reading - ``EFAULT``: the caller provided inaccessible memory - ``ENODATA``: the file is not a verity file - ``ENOTTY``: this type of filesystem does not implement fs-verity @@ -310,6 +312,7 @@ blocks from disk without actually verifying the path to the root node. FS_IOC_READ_VERITY_METADATA can fail with the following errors: +- ``EBADF``: the file descriptor is not open for reading - ``EFAULT``: the caller provided inaccessible memory - ``EINTR``: the ioctl was interrupted before any data was read - ``EINVAL``: reserved fields were set, or ``offset + length`` diff --git a/fs/verity/measure.c b/fs/verity/measure.c index 433d963edf3bb..5ec36d845008b 100644 --- a/fs/verity/measure.c +++ b/fs/verity/measure.c @@ -31,6 +31,16 @@ int fsverity_ioctl_measure(struct file *filp, void __user *_uarg) const struct fsverity_hash_alg *hash_alg; struct fsverity_digest arg; + /* + * This ioctl returns a hash of the file contents, so it should require + * read permission. Disallow it on ioctl-only (i.e., nonstandard access + * mode 3) fds, which can in some cases be acquired without passing all + * LSM read-permission checks. Also disallow write-only fds, which can + * refer only to non-verity files which would fail with ENODATA anyway. + */ + if (!(filp->f_mode & FMODE_READ)) + return -EBADF; + vi = fsverity_get_info(inode); if (!vi) return -ENODATA; /* not a verity file */ diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c index cba5d6af4e04f..cfe9227a41c45 100644 --- a/fs/verity/read_metadata.c +++ b/fs/verity/read_metadata.c @@ -157,13 +157,19 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) int length; void __user *buf; + /* + * This ioctl returns file contents block hashes, so it should require + * read permission. Disallow it on ioctl-only (i.e., nonstandard access + * mode 3) fds, which can in some cases be acquired without passing all + * LSM read-permission checks. Also disallow write-only fds, which can + * refer only to non-verity files which would fail with ENODATA anyway. + */ + if (!(filp->f_mode & FMODE_READ)) + return -EBADF; + vi = fsverity_get_info(inode); if (!vi) return -ENODATA; /* not a verity file */ - /* - * Note that we don't have to explicitly check that the file is open for - * reading, since verity files can only be opened for reading. - */ if (copy_from_user(&arg, uarg, sizeof(arg))) return -EFAULT; -- 2.53.0