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=1794078568; b=rHepA0zrd1JQR7x1BnL7VBnSGv2gLx1y3wTNa86GpOGkb+6ShQQWSgX+PgOBgJaJPp4F PSa7kDSAIWGG8YlhX6MdfX1W0HT/uFODuIBB3F3Lqp/ys7y8UUHMKsVxokX1U1IKzo7vM UlRwNPDmevdYvqLbYCXKMaZvYFD22L08mXwnOWNlvqxNNINddL1CdH0xoi1/jzX+5vbAm DN6AQyospT3oypsE1PL8wTKM2C4zvWUUBncma2QhVd/G0prgE9Nv4xvWQEeVf6kRPc+m1 ZKkSxKJ4ZJ6KWmkdYYswt7XoQEcaiWMjIKzzcf7rIIdVPTHKWypTRast8Jo8C+NzDiw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794078568; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Transfer-Encoding; bh=24dbhxFaoUxvMo1MTSlMsDk12vx2NxNcSYESx7/jpvI=; b=AQAm15w+LdqqTh9gEs07mtrPFxM04/OgYbCapISGdykWXre0UYZAY4Vzy8TZL8rE6Jez hqIdMDAgBP2hKkk3+c/CyAlhNJakU4HSyPOZzgUDqAZWVlaoTLzyFQTZiWRrWXVN5Mo/k z/m/klMM29qXfBHq0KkU6zcvyeE1rWV73fTjGrpDl4xk04nRah3u8w58rc1CIsuNJcIdx wcJegSTqSnLytxXLZuJHifvrFfuEcc+tWogL07uKNbKD4DeJB15aaaPucQYYZt35Hv8x+ QYpwllUGdxcRq2j7wvxiNmPMkRWDmmt7XMy2HW2rAsfaw+JDg4M7KkEUlb7ithj/3cQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=G7qXfkQm; 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 1D755606A32D; Sat, 7 Nov 2026 19:09:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=G7qXfkQm Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8200B1F0089F; Sat, 7 Nov 2026 19:09:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794078567; bh=24dbhxFaoUxvMo1MTSlMsDk12vx2NxNcSYESx7/jpvI=; h=From:To:Cc:Subject:Date; b=G7qXfkQmSWr6KXoMf7wFIAX04stRRaL+ltL7+JSYArC6N+vUh2hihXY94wkgs4bTm wFGL8VShASbkgAGQoJtis+lImLqb9IJG3ixkd6b2PHnFFBLmf66/M8ifXeRbmvA2g6 n8KGgKqYn6Ujvho391RK8h2SqPGmH/VeSjUMrwQG547Zh7pGZAggddF2AGlcNOIqLm 6wcDYkd0cFFJWiFKlB38rpwllRWVSIUlKWwy89th9jR3vkiN2mF0Fe3np2dqpDy3FL rRzoBy5SW6D9azEezkY/WCKL3nGoeUvyw+TXN2b473SxnGOFQ3lsB1Xh+Znw9xxUcY 7gf5NOgWXCcaw== From: Eric Biggers To: stable@vger.kernel.org Cc: fsverity@lists.linux.dev, Eric Biggers , Andrey Albershteyn Subject: [PATCH 6.12] fsverity: Explicitly require FMODE_READ to retrieve hashes Date: Sat, 7 Nov 2026 11:09:12 -0800 Message-ID: <20261107190912.16192-1-ebiggers@kernel.org> X-Mailer: git-send-email 2.56.0 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 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 --- 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 0e2fac7a16da1..f879e052d4ecc 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 @@ -233,6 +234,7 @@ 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 @@ -305,6 +307,7 @@ 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 91ce39ced77b8..b5af400c725e8 100644 --- a/fs/verity/measure.c +++ b/fs/verity/measure.c @@ -30,6 +30,16 @@ 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 f58432772d9ea..680792701ba29 100644 --- a/fs/verity/read_metadata.c +++ b/fs/verity/read_metadata.c @@ -156,13 +156,19 @@ 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; base-commit: 5c40a1750f44dd6c7292d8c8d0b4ffff1734576e -- 2.56.0