linux-ext4 - [PATCH 5/5] vfs: only allow FSSETXATTR to set DAX flag on files and dirs

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Date:   Fri, 28 Jun 2019 11:34:31 -0700
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     matthew.garrett@...ula.com, yuchao0@...wei.com, tytso@....edu,
        darrick.wong@...cle.com, shaggy@...nel.org,
        ard.biesheuvel@...aro.org, josef@...icpanda.com, hch@...radead.org,
        clm@...com, adilger.kernel@...ger.ca, jk@...abs.org, jack@...e.com,
        dsterba@...e.com, jaegeuk@...nel.org, viro@...iv.linux.org.uk
Cc:     cluster-devel@...hat.com, jfs-discussion@...ts.sourceforge.net,
        linux-efi@...r.kernel.org, reiserfs-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-xfs@...r.kernel.org,
        linux-nilfs@...r.kernel.org, linux-mtd@...ts.infradead.org,
        ocfs2-devel@....oracle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: [PATCH 5/5] vfs: only allow FSSETXATTR to set DAX flag on files and
 dirs

From: Darrick J. Wong <darrick.wong@...cle.com>

The DAX flag only applies to files and directories, so don't let it get
set for other types of files.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 fs/inode.c |    8 ++++++++
 1 file changed, 8 insertions(+)


diff --git a/fs/inode.c b/fs/inode.c
index 670d5408d022..f08711b34341 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2259,6 +2259,14 @@ int vfs_ioc_fssetxattr_check(struct inode *inode, const struct fsxattr *old_fa,
 	    !S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 		return -EINVAL;
 
+	/*
+	 * It is only valid to set the DAX flag on regular files and
+	 * directories on filesystems.
+	 */
+	if ((fa->fsx_xflags & FS_XFLAG_DAX) &&
+	    !(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode)))
+		return -EINVAL;
+
 	/* Extent size hints of zero turn off the flags. */
 	if (fa->fsx_extsize == 0)
 		fa->fsx_xflags &= ~(FS_XFLAG_EXTSIZE | FS_XFLAG_EXTSZINHERIT);