From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C65B246EC77; Tue, 21 Jul 2026 18:44:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784659468; cv=none; b=Xv8ydbkTRlLRaOicJLunO/IoBIw6CFt6lQ91fsXkyqJqkzNZWRkVP80yWfS9VJFAr8wAtRp6q3uGrYrxMrC47G+8rLmvs9mkjkvnym9EBJraBZQIQQR+X9zcYUbcTwtrmvN5diL94+43ZulyNjwSRO6gh2R+RCwdiU9AeAzvqPM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784659468; c=relaxed/simple; bh=Wy5o9OnRMNvwtQA5xGH9N2exQqBqFF6O/O6bRhznn5Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=jLimuJYt848xKwGR6J9HhDgWobUFTke/OwRA8usPcxppOD3WlI5kqcRZsxCMKaT37xMvNd3ymsy1Qv0a+QEmkQUibtrNQm7+7uA3vLjWCqdgl0/j+5k4km1CjVLrHZn8VtJH3xTkyHiI3c9Q5Ep6ZjjC6qT5GIvJBhPYMwSyXX4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TrwJyO8e; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TrwJyO8e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3125B1F00A3D; Tue, 21 Jul 2026 18:44:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784659467; bh=+tD0Us9sn7wTap8Za5kiVDiU+2D9hhY3YmsPKt5bTSM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TrwJyO8eLxeCLhLyhnL4zLsM5PhSM1wulFC0qouFrNwCPPpousRa1vcxyUjKHt2dB WTfHJ9GkrQIsMG9NHKtZzVpOza2B8x60/GmankpyVxevWD+V4F9qgMMsjTqZDnaL6V XWzTPv5ZjkG4r0//Gwms2saWgRNARqId3GAYHex5Rd7ILcDx2iWbUuui3NxAhf2qJS 5/11oxxHTY23bV47/dbxbjHftXv1G/4Fh3TVBouhHI9I4+hSNOwB8tKNYOlm1lOttF alaiYWOPrzHQrQ9GLfH3Et5wRukk0pTF7bWPyamuoYnoP/qnuySDUPfrMyZ0pilLVl OmiJcZNBfYhPA== From: Andrey Albershteyn To: linux-xfs@vger.kernel.org, fsverity@lists.linux.dev, linux-fsdevel@vger.kernel.org, ebiggers@kernel.org Cc: Andrey Albershteyn , hch@lst.de, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-btrfs@vger.kernel.org, djwong@kernel.org Subject: [PATCH v13 11/23] xfs: disable direct read path for fs-verity files Date: Tue, 21 Jul 2026 20:40:48 +0200 Message-ID: <20260721184346.416657-12-aalbersh@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260721184346.416657-1-aalbersh@kernel.org> References: <20260721184346.416657-1-aalbersh@kernel.org> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The direct path is not supported on verity files. Attempts to use direct I/O path on such files should fall back to buffered I/O path. Add a fall back to buffered I/O at two place, in a common fast path and latter when lock is acquired. The second check prevents TOCTOU issue with reading fsverity_active() status and resetting IOCB_DIRECT flag. If one thread saw fsverity_active() to be false, and then second thread acquired XFS_IOLOCK_EXCL and enabled fsverity. The first thread will go through the DIO path. Signed-off-by: Darrick J. Wong Signed-off-by: Andrey Albershteyn --- fs/xfs/xfs_file.c | 59 +++++++++++++++++++++++++++++++---------------- 1 file changed, 39 insertions(+), 20 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index 845a97c9b063..f7e3fe22ca96 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -245,6 +245,25 @@ static const struct iomap_dio_ops xfs_dio_read_bounce_ops = { .bio_set = &iomap_ioend_bioset, }; +STATIC ssize_t +xfs_file_buffered_read( + struct kiocb *iocb, + struct iov_iter *to) +{ + struct xfs_inode *ip = XFS_I(file_inode(iocb->ki_filp)); + ssize_t ret; + + trace_xfs_file_buffered_read(iocb, to); + + ret = xfs_ilock_iocb(iocb, XFS_IOLOCK_SHARED); + if (ret) + return ret; + ret = generic_file_read_iter(iocb, to); + xfs_iunlock(ip, XFS_IOLOCK_SHARED); + + return ret; +} + STATIC ssize_t xfs_file_dio_read( struct kiocb *iocb, @@ -265,6 +284,16 @@ xfs_file_dio_read( ret = xfs_ilock_iocb(iocb, XFS_IOLOCK_SHARED); if (ret) return ret; + /* + * Re-check verity status after acquiring lock. This prevents TOCTOU in + * xfs_file_read_iter() while falling back from DIO to buffered I/O as + * now we are holding a lock + */ + if (fsverity_active(VFS_I(ip))) { + xfs_iunlock(ip, XFS_IOLOCK_SHARED); + iocb->ki_flags &= ~IOCB_DIRECT; + return xfs_file_buffered_read(iocb, to); + } if (mapping_stable_writes(iocb->ki_filp->f_mapping)) { dio_ops = &xfs_dio_read_bounce_ops; dio_flags |= IOMAP_DIO_BOUNCE; @@ -281,7 +310,8 @@ xfs_file_dax_read( struct kiocb *iocb, struct iov_iter *to) { - struct xfs_inode *ip = XFS_I(iocb->ki_filp->f_mapping->host); + struct inode *inode = iocb->ki_filp->f_mapping->host; + struct xfs_inode *ip = XFS_I(inode); ssize_t ret = 0; trace_xfs_file_dax_read(iocb, to); @@ -299,25 +329,6 @@ xfs_file_dax_read( return ret; } -STATIC ssize_t -xfs_file_buffered_read( - struct kiocb *iocb, - struct iov_iter *to) -{ - struct xfs_inode *ip = XFS_I(file_inode(iocb->ki_filp)); - ssize_t ret; - - trace_xfs_file_buffered_read(iocb, to); - - ret = xfs_ilock_iocb(iocb, XFS_IOLOCK_SHARED); - if (ret) - return ret; - ret = generic_file_read_iter(iocb, to); - xfs_iunlock(ip, XFS_IOLOCK_SHARED); - - return ret; -} - STATIC ssize_t xfs_file_read_iter( struct kiocb *iocb, @@ -332,6 +343,14 @@ xfs_file_read_iter( if (xfs_is_shutdown(mp)) return -EIO; + /* + * In case fs-verity is enabled, we also fallback to the buffered read + * from the direct read path. Therefore, IOCB_DIRECT is set and need to + * be cleared (see generic_file_read_iter()) + */ + if (fsverity_active(inode)) + iocb->ki_flags &= ~IOCB_DIRECT; + if (IS_DAX(inode)) ret = xfs_file_dax_read(iocb, to); else if (iocb->ki_flags & IOCB_DIRECT) -- 2.54.0