xfs: enforce metadata inode flag

Add checks for the metadata inode flag so that we don't ever leak
metadata inodes out to userspace, and we don't ever try to read a
regular inode as metadata.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 70 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 78febaa0d692..424861fbf1bd 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -19,6 +19,7 @@
 #include "xfs_ialloc.h"
 #include "xfs_dir2.h"
 #include "xfs_health.h"
+#include "xfs_metafile.h"
 
 #include <linux/iversion.h>
 
@@ -489,6 +490,69 @@ xfs_dinode_verify_nrext64(
 	return NULL;
 }
 
+/*
+ * Validate all the picky requirements we have for a file that claims to be
+ * filesystem metadata.
+ */
+xfs_failaddr_t
+xfs_dinode_verify_metadir(
+	struct xfs_mount	*mp,
+	struct xfs_dinode	*dip,
+	uint16_t		mode,
+	uint16_t		flags,
+	uint64_t		flags2)
+{
+	if (!xfs_has_metadir(mp))
+		return __this_address;
+
+	/* V5 filesystem only */
+	if (dip->di_version < 3)
+		return __this_address;
+
+	if (be16_to_cpu(dip->di_metatype) >= XFS_METAFILE_MAX)
+		return __this_address;
+
+	/* V3 inode fields that are always zero */
+	if ((flags2 & XFS_DIFLAG2_NREXT64) && dip->di_nrext64_pad)
+		return __this_address;
+	if (!(flags2 & XFS_DIFLAG2_NREXT64) && dip->di_flushiter)
+		return __this_address;
+
+	/* Metadata files can only be directories or regular files */
+	if (!S_ISDIR(mode) && !S_ISREG(mode))
+		return __this_address;
+
+	/* They must have zero access permissions */
+	if (mode & 0777)
+		return __this_address;
+
+	/* DMAPI event and state masks are zero */
+	if (dip->di_dmevmask || dip->di_dmstate)
+		return __this_address;
+
+	/*
+	 * User and group IDs must be zero.  The project ID is used for
+	 * grouping inodes.  Metadata inodes are never accounted to quotas.
+	 */
+	if (dip->di_uid || dip->di_gid)
+		return __this_address;
+
+	/* Mandatory inode flags must be set */
+	if (S_ISDIR(mode)) {
+		if ((flags & XFS_METADIR_DIFLAGS) != XFS_METADIR_DIFLAGS)
+			return __this_address;
+	} else {
+		if ((flags & XFS_METAFILE_DIFLAGS) != XFS_METAFILE_DIFLAGS)
+			return __this_address;
+	}
+
+	/* dax flags2 must not be set */
+	if (flags2 & XFS_DIFLAG2_DAX)
+		return __this_address;
+
+	return NULL;
+}
+
 xfs_failaddr_t
 xfs_dinode_verify(
 	struct xfs_mount	*mp,
@@ -673,6 +737,12 @@ xfs_dinode_verify(
 	    !xfs_has_bigtime(mp))
 		return __this_address;
 
+	if (flags2 & XFS_DIFLAG2_METADATA) {
+		fa = xfs_dinode_verify_metadir(mp, dip, mode, flags, flags2);
+		if (fa)
+			return fa;
+	}
+
 	return NULL;
 }