[PATCH 07/28] xfs: enforce metadata inode flag

Darrick J. Wong
2024-10-11T00:50:13Z

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>
---
fs/xfs/libxfs/xfs_inode_buf.c | 70 +++++++++++++++++++++++++++++++++++++++++
fs/xfs/libxfs/xfs_inode_buf.h | 3 ++
fs/xfs/libxfs/xfs_metafile.h | 11 ++++++
fs/xfs/scrub/common.c | 10 +++++-
fs/xfs/scrub/inode.c | 26 ++++++++++++++-
fs/xfs/scrub/inode_repair.c | 10 ++++++
fs/xfs/xfs_icache.c | 9 +++++
fs/xfs/xfs_inode.c | 11 ++++++
8 files changed, 145 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index cdd6ed4279649d..bdccdf81ac9eba 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>

@@ -488,6 +489,69 @@ 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,
@@ -672,6 +736,12 @@ 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;
}

diff --git a/fs/xfs/libxfs/xfs_inode_buf.h b/fs/xfs/libxfs/xfs_inode_buf.h
index 585ed5a110af4e..8d43d2641c7328 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.h
+++ b/fs/xfs/libxfs/xfs_inode_buf.h
@@ -28,6 +28,9 @@ int xfs_inode_from_disk(struct xfs_inode *ip, struct xfs_dinode *from);

xfs_failaddr_t xfs_dinode_verify(struct xfs_mount *mp, xfs_ino_t ino,
struct xfs_dinode *dip);
+xfs_failaddr_t xfs_dinode_verify_metadir(struct xfs_mount *mp,
+ struct xfs_dinode *dip, uint16_t mode, uint16_t flags,
+ uint64_t flags2);
xfs_failaddr_t xfs_inode_validate_extsize(struct xfs_mount *mp,
uint32_t extsize, uint16_t mode, uint16_t flags);
xfs_failaddr_t xfs_inode_validate_cowextsize(struct xfs_mount *mp,
diff --git a/fs/xfs/libxfs/xfs_metafile.h b/fs/xfs/libxfs/xfs_metafile.h
index 60fe1890611277..c66b0c51b461a8 100644
--- a/fs/xfs/libxfs/xfs_metafile.h
+++ b/fs/xfs/libxfs/xfs_metafile.h
@@ -6,6 +6,17 @@
#ifndef __XFS_METAFILE_H__
#define __XFS_METAFILE_H__

+/* All metadata files must have these flags set. */
+#define XFS_METAFILE_DIFLAGS (XFS_DIFLAG_IMMUTABLE | \
+ XFS_DIFLAG_SYNC | \
+ XFS_DIFLAG_NOATIME | \
+ XFS_DIFLAG_NODUMP | \
+ XFS_DIFLAG_NODEFRAG)
+
+/* All metadata directories must have these flags set. */
+#define XFS_METADIR_DIFLAGS (XFS_METAFILE_DIFLAGS | \
+ XFS_DIFLAG_NOSYMLINKS)
+
/* Code specific to kernel/userspace; must be provided externally. */

int xfs_trans_metafile_iget(struct xfs_trans *tp, xfs_ino_t ino,
diff --git a/fs/xfs/scrub/common.c b/fs/xfs/scrub/common.c
index b71768c2a8c129..9d74c315418ffb 100644
--- a/fs/xfs/scrub/common.c
+++ b/fs/xfs/scrub/common.c
@@ -947,9 +947,15 @@ xchk_iget_for_scrubbing(
if (sc->sm->sm_ino == 0 || sc->sm->sm_ino == ip_in->i_ino)
return xchk_install_live_inode(sc, ip_in);

- /* Reject internal metadata files and obviously bad inode numbers. */
- if (xfs_internal_inum(mp, sc->sm->sm_ino))
+ /*
+ * On pre-metadir filesystems, reject internal metadata files. For
+ * metadir filesystems, limited scrubbing of any file in the metadata
+ * directory tree by handle is allowed, because that is the only way to
+ * validate the lack of parent pointers in the sb-root metadata inodes.
+ */
+ if (!xfs_has_metadir(mp) && xfs_internal_inum(mp, sc->sm->sm_ino))
return -ENOENT;
+ /* Reject obviously bad inode numbers. */
if (!xfs_verify_ino(sc->mp, sc->sm->sm_ino))
return -ENOENT;

diff --git a/fs/xfs/scrub/inode.c b/fs/xfs/scrub/inode.c
index ec2c694c4083f8..45222552a51ccb 100644
--- a/fs/xfs/scrub/inode.c
+++ b/fs/xfs/scrub/inode.c
@@ -60,6 +60,22 @@ xchk_install_handle_iscrub(
if (error)
return error;

+ /*
+ * Don't allow scrubbing by handle of any non-directory inode records
+ * in the metadata directory tree. We don't know if any of the scans
+ * launched by this scrubber will end up indirectly trying to lock this
+ * file.
+ *
+ * Scrubbers of inode-rooted metadata files (e.g. quota files) will
+ * attach all the resources needed to scrub the inode and call
+ * xchk_inode directly. Userspace cannot call this directly.
+ */
+ if (xfs_is_metadir_inode(ip) && !S_ISDIR(VFS_I(ip)->i_mode)) {
+ xchk_irele(sc, ip);
+ sc->ip = NULL;
+ return -ENOENT;
+ }
+
return xchk_prepare_iscrub(sc);
}

@@ -94,9 +110,15 @@ xchk_setup_inode(
return xchk_prepare_iscrub(sc);
}

- /* Reject internal metadata files and obviously bad inode numbers. */
- if (xfs_internal_inum(mp, sc->sm->sm_ino))
+ /*
+ * On pre-metadir filesystems, reject internal metadata files. For
+ * metadir filesystems, limited scrubbing of any file in the metadata
+ * directory tree by handle is allowed, because that is the only way to
+ * validate the lack of parent pointers in the sb-root metadata inodes.
+ */
+ if (!xfs_has_metadir(mp) && xfs_internal_inum(mp, sc->sm->sm_ino))
return -ENOENT;
+ /* Reject obviously bad inode numbers. */
if (!xfs_verify_ino(sc->mp, sc->sm->sm_ino))
return -ENOENT;

diff --git a/fs/xfs/scrub/inode_repair.c b/fs/xfs/scrub/inode_repair.c
index fdc2f0d058d557..1a7d2dfc2f405d 100644
--- a/fs/xfs/scrub/inode_repair.c
+++ b/fs/xfs/scrub/inode_repair.c
@@ -568,6 +568,16 @@ xrep_dinode_flags(
dip->di_nrext64_pad = 0;
else if (dip->di_version >= 3)
dip->di_v3_pad = 0;
+
+ if (flags2 & XFS_DIFLAG2_METADATA) {
+ xfs_failaddr_t fa;
+
+ fa = xfs_dinode_verify_metadir(sc->mp, dip, mode, flags,
+ flags2);
+ if (fa)
+ flags2 &= ~XFS_DIFLAG2_METADATA;
+ }
+
dip->di_flags = cpu_to_be16(flags);
dip->di_flags2 = cpu_to_be64(flags2);
}
diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 8b78ca1eb8fa69..1709abafe6000e 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -863,13 +863,20 @@ xfs_trans_metafile_iget(
mode = S_IFREG;
if (inode_wrong_type(VFS_I(ip), mode))
goto bad_rele;
+ if (xfs_has_metadir(mp)) {
+ if (!xfs_is_metadir_inode(ip))
+ goto bad_rele;
+ if (metafile_type != ip->i_metatype)
+ goto bad_rele;
+ }

*ipp = ip;
return 0;
bad_rele:
xfs_irele(ip);
whine:
- xfs_err(mp, "metadata inode 0x%llx is corrupt", ino);
+ xfs_err(mp, "metadata inode 0x%llx type %u is corrupt", ino,
+ metafile_type);
return -EFSCORRUPTED;
}

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 87975b730eae23..752a4d39d5cc4f 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -555,8 +555,19 @@ xfs_lookup(
if (error)
goto out_free_name;

+ /*
+ * Fail if a directory entry in the regular directory tree points to
+ * a metadata file.
+ */
+ if (XFS_IS_CORRUPT(dp->i_mount, xfs_is_metadir_inode(*ipp))) {
+ error = -EFSCORRUPTED;
+ goto out_irele;
+ }
+
return 0;

+out_irele:
+ xfs_irele(*ipp);
out_free_name:
if (ci_name)
kfree(ci_name->name);