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 F13253C4555; Fri, 2 Oct 2026 22:37:44 +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=1790980666; cv=none; b=KROuIukow9A1YnousqKuI+jnkNHVsG7IY+m5yPfDS8kA0PMKdxQAdL2XE80dKkAIjaGRDVktYV56S5lS+VfVst0V6y9UBN+KF6uJjUfXoylYsuzG5I3NNHA48y8ZrHiqdp2ge7gF9RklxiAavtpGZDW4QAgIGeZMjMRYdynhOck= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790980666; c=relaxed/simple; bh=T8QaJnUp0BFUpEp0YiOa+PckWORguMtKwkHNvRCfbeY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cGEfsGOvvZ0f1yliHwI6E4LMSFXxLefDCpfSfC+Yv5ZDDonxxtar0G8UgVhDkjXJQHj+YD1Grb3u4wK4SsduTt7ZURPvM9af2ja1KyztYzrPte8gvPuEDdUBDxmPjY6ZVBDXk1Lwrdupp3cOvMd2aTryyHudqlHvHnmZnYgdnrg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aE8cWwJu; 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="aE8cWwJu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8B0251F00893; Fri, 2 Oct 2026 22:37:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790980664; bh=V/xMdTPkYwWHhaiHtNRdjWuqquaN/UDdlep3XfzYfiw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aE8cWwJuQNVQUvEZa9dP1qgvQ5tnUowl9bA37rROte8G+MhGqEHmneOPCiZc/+xgM WsIz3hWRkcRZWiRIMGMOAzTXHvN8dGaiwyX2W+NQcj8q1iG1I7IEFRxrjgdujXWvDE N0/345qRxjhlGa30R0qzkxhIuO8fPgB2lW6U4HAhcYwQQfLZjwgUDO0YjmsGP9go4M PTiOkEnArREa+yngNUKpziNTxiJFqB/eKdKqBs2ZjsAcbpU27ubSyYUR0aQH25H+mv ePOwFYb1uu7zX2RheziOIJw5N+slBgzbach85qEprWRIbrcUg8Bd/pa2hW+LVF87mb 54O40WZgoxsGw== From: Andrey Albershteyn To: djwong@kernel.org, ebiggers@kernel.org, hch@lst.de, Carlos Maiolino Cc: Andrey Albershteyn , fsverity@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-btrfs@vger.kernel.org, david@fromorbit.com Subject: [PATCH v17 09/21] xfs: disable direct read path for fs-verity files Date: Sat, 3 Oct 2026 00:36:50 +0200 Message-ID: <20261002223705.2175542-10-aalbersh@kernel.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20261002223705.2175542-1-aalbersh@kernel.org> References: <20261002223705.2175542-1-aalbersh@kernel.org> Precedence: bulk X-Mailing-List: linux-fsdevel@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 Reviewed-by: Christoph Hellwig --- fs/xfs/xfs_file.c | 61 +++++++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 20 deletions(-) diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c index dd3782e9af93..07abf6e8783f 100644 --- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -38,6 +38,7 @@ #include #include #include +#include static const struct vm_operations_struct xfs_file_vm_ops; @@ -232,6 +233,25 @@ 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, @@ -250,6 +270,17 @@ 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)) { ret = iomap_dio_rw(iocb, to, &xfs_read_iomap_ops, &xfs_dio_read_bounce_ops, 0, NULL, 0); @@ -269,7 +300,8 @@ 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); @@ -287,25 +319,6 @@ 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, @@ -320,6 +333,14 @@ 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