xfs: verify inline directory data forks

Source kernel commit: 630a04e79dd41ff746b545d4fc052e0abb836120

When we're reading or writing the data fork of an inline directory,
check the contents to make sure we're not overflowing buffers or eating
garbage data.  xfs/348 corrupts an inline symlink into an inline
directory, triggering a buffer overflow bug.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

4 files changed, 113 insertions, 4 deletions

diff --git a/libxfs/xfs_dir2_priv.h b/libxfs/xfs_dir2_priv.h
index d04547fcf2..eb00bc133b 100644
--- a/libxfs/xfs_dir2_priv.h
+++ b/libxfs/xfs_dir2_priv.h
@@ -125,6 +125,8 @@ extern int xfs_dir2_sf_create(struct xfs_da_args *args, xfs_ino_t pino);
 extern int xfs_dir2_sf_lookup(struct xfs_da_args *args);
 extern int xfs_dir2_sf_removename(struct xfs_da_args *args);
 extern int xfs_dir2_sf_replace(struct xfs_da_args *args);
+extern int xfs_dir2_sf_verify(struct xfs_mount *mp, struct xfs_dir2_sf_hdr *sfp,
+		int size);
 
 /* xfs_dir2_readdir.c */
 extern int xfs_readdir(struct xfs_inode *dp, struct dir_context *ctx,
diff --git a/libxfs/xfs_dir2_sf.c b/libxfs/xfs_dir2_sf.c
index 0b1f175054..712afa5ccb 100644
--- a/libxfs/xfs_dir2_sf.c
+++ b/libxfs/xfs_dir2_sf.c
@@ -627,6 +627,93 @@ xfs_dir2_sf_check(
 }
 #endif	/* DEBUG */
 
+/* Verify the consistency of an inline directory. */
+int
+xfs_dir2_sf_verify(
+	struct xfs_mount		*mp,
+	struct xfs_dir2_sf_hdr		*sfp,
+	int				size)
+{
+	struct xfs_dir2_sf_entry	*sfep;
+	struct xfs_dir2_sf_entry	*next_sfep;
+	char				*endp;
+	const struct xfs_dir_ops	*dops;
+	xfs_ino_t			ino;
+	int				i;
+	int				i8count;
+	int				offset;
+	__uint8_t			filetype;
+
+	dops = xfs_dir_get_ops(mp, NULL);
+
+	/*
+	 * Give up if the directory is way too short.
+	 */
+	XFS_WANT_CORRUPTED_RETURN(mp, size >
+			offsetof(struct xfs_dir2_sf_hdr, parent));
+	XFS_WANT_CORRUPTED_RETURN(mp, size >=
+			xfs_dir2_sf_hdr_size(sfp->i8count));
+
+	endp = (char *)sfp + size;
+
+	/* Check .. entry */
+	ino = dops->sf_get_parent_ino(sfp);
+	i8count = ino > XFS_DIR2_MAX_SHORT_INUM;
+	XFS_WANT_CORRUPTED_RETURN(mp, !xfs_dir_ino_validate(mp, ino));
+	offset = dops->data_first_offset;
+
+	/* Check all reported entries */
+	sfep = xfs_dir2_sf_firstentry(sfp);
+	for (i = 0; i < sfp->count; i++) {
+		/*
+		 * struct xfs_dir2_sf_entry has a variable length.
+		 * Check the fixed-offset parts of the structure are
+		 * within the data buffer.
+		 */
+		XFS_WANT_CORRUPTED_RETURN(mp,
+				((char *)sfep + sizeof(*sfep)) < endp);
+
+		/* Don't allow names with known bad length. */
+		XFS_WANT_CORRUPTED_RETURN(mp, sfep->namelen > 0);
+		XFS_WANT_CORRUPTED_RETURN(mp, sfep->namelen < MAXNAMELEN);
+
+		/*
+		 * Check that the variable-length part of the structure is
+		 * within the data buffer.  The next entry starts after the
+		 * name component, so nextentry is an acceptable test.
+		 */
+		next_sfep = dops->sf_nextentry(sfp, sfep);
+		XFS_WANT_CORRUPTED_RETURN(mp, endp >= (char *)next_sfep);
+
+		/* Check that the offsets always increase. */
+		XFS_WANT_CORRUPTED_RETURN(mp,
+				xfs_dir2_sf_get_offset(sfep) >= offset);
+
+		/* Check the inode number. */
+		ino = dops->sf_get_ino(sfp, sfep);
+		i8count += ino > XFS_DIR2_MAX_SHORT_INUM;
+		XFS_WANT_CORRUPTED_RETURN(mp, !xfs_dir_ino_validate(mp, ino));
+
+		/* Check the file type. */
+		filetype = dops->sf_get_ftype(sfep);
+		XFS_WANT_CORRUPTED_RETURN(mp, filetype < XFS_DIR3_FT_MAX);
+
+		offset = xfs_dir2_sf_get_offset(sfep) +
+				dops->data_entsize(sfep->namelen);
+
+		sfep = next_sfep;
+	}
+	XFS_WANT_CORRUPTED_RETURN(mp, i8count == sfp->i8count);
+	XFS_WANT_CORRUPTED_RETURN(mp, (void *)sfep == (void *)endp);
+
+	/* Make sure this whole thing ought to be in local format. */
+	XFS_WANT_CORRUPTED_RETURN(mp, offset +
+	       (sfp->count + 2) * (uint)sizeof(xfs_dir2_leaf_entry_t) +
+	       (uint)sizeof(xfs_dir2_block_tail_t) <= mp->m_dir_geo->blksize);
+
+	return 0;
+}
+
 /*
  * Create a new (shortform) directory.
  */
diff --git a/libxfs/xfs_inode_fork.c b/libxfs/xfs_inode_fork.c
index 8df1d337b8..cc7f36bf59 100644
--- a/libxfs/xfs_inode_fork.c
+++ b/libxfs/xfs_inode_fork.c
@@ -29,6 +29,8 @@
 #include "xfs_trace.h"
 #include "xfs_attr_sf.h"
 #include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_dir2_priv.h"
 
 
 kmem_zone_t *xfs_ifork_zone;
@@ -317,6 +319,7 @@ xfs_iformat_local(
 	int		whichfork,
 	int		size)
 {
+	int		error;
 
 	/*
 	 * If the size is unreasonable, then something
@@ -333,6 +336,14 @@ xfs_iformat_local(
 		return -EFSCORRUPTED;
 	}
 
+	if (S_ISDIR(VFS_I(ip)->i_mode) && whichfork == XFS_DATA_FORK) {
+		error = xfs_dir2_sf_verify(ip->i_mount,
+				(struct xfs_dir2_sf_hdr *)XFS_DFORK_DPTR(dip),
+				size);
+		if (error)
+			return error;
+	}
+
 	xfs_init_local_fork(ip, whichfork, XFS_DFORK_PTR(dip, whichfork), size);
 	return 0;
 }
@@ -853,7 +864,7 @@ xfs_iextents_copy(
  * In these cases, the format always takes precedence, because the
  * format indicates the current state of the fork.
  */
-void
+int
 xfs_iflush_fork(
 	xfs_inode_t		*ip,
 	xfs_dinode_t		*dip,
@@ -863,6 +874,7 @@ xfs_iflush_fork(
 	char			*cp;
 	xfs_ifork_t		*ifp;
 	xfs_mount_t		*mp;
+	int			error;
 	static const short	brootflag[2] =
 		{ XFS_ILOG_DBROOT, XFS_ILOG_ABROOT };
 	static const short	dataflag[2] =
@@ -871,7 +883,7 @@ xfs_iflush_fork(
 		{ XFS_ILOG_DEXT, XFS_ILOG_AEXT };
 
 	if (!iip)
-		return;
+		return 0;
 	ifp = XFS_IFORK_PTR(ip, whichfork);
 	/*
 	 * This can happen if we gave up in iformat in an error path,
@@ -879,12 +891,19 @@ xfs_iflush_fork(
 	 */
 	if (!ifp) {
 		ASSERT(whichfork == XFS_ATTR_FORK);
-		return;
+		return 0;
 	}
 	cp = XFS_DFORK_PTR(dip, whichfork);
 	mp = ip->i_mount;
 	switch (XFS_IFORK_FORMAT(ip, whichfork)) {
 	case XFS_DINODE_FMT_LOCAL:
+		if (S_ISDIR(VFS_I(ip)->i_mode) && whichfork == XFS_DATA_FORK) {
+			error = xfs_dir2_sf_verify(mp,
+					(struct xfs_dir2_sf_hdr *)ifp->if_u1.if_data,
+					ifp->if_bytes);
+			if (error)
+				return error;
+		}
 		if ((iip->ili_fields & dataflag[whichfork]) &&
 		    (ifp->if_bytes > 0)) {
 			ASSERT(ifp->if_u1.if_data != NULL);
@@ -937,6 +956,7 @@ xfs_iflush_fork(
 		ASSERT(0);
 		break;
 	}
+	return 0;
 }
 
 /*
diff --git a/libxfs/xfs_inode_fork.h b/libxfs/xfs_inode_fork.h
index 7fb8365326..132dc59fdd 100644
--- a/libxfs/xfs_inode_fork.h
+++ b/libxfs/xfs_inode_fork.h
@@ -140,7 +140,7 @@ typedef struct xfs_ifork {
 struct xfs_ifork *xfs_iext_state_to_fork(struct xfs_inode *ip, int state);
 
 int		xfs_iformat_fork(struct xfs_inode *, struct xfs_dinode *);
-void		xfs_iflush_fork(struct xfs_inode *, struct xfs_dinode *,
+int		xfs_iflush_fork(struct xfs_inode *, struct xfs_dinode *,
 				struct xfs_inode_log_item *, int);
 void		xfs_idestroy_fork(struct xfs_inode *, int);
 void		xfs_idata_realloc(struct xfs_inode *, int, int);