xfs: create structure verifier function for shortform xattrs

Source kernel commit: 1e1bbd8e7ee0624034e9bf1e91ac11a7aaa2f8a6

Create a function to perform structure verification for short form
extended attributes.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

4 files changed, 83 insertions, 0 deletions

diff --git a/libxfs/libxfs_priv.h b/libxfs/libxfs_priv.h
index eef344bb51..130f6ed2bb 100644
--- a/libxfs/libxfs_priv.h
+++ b/libxfs/libxfs_priv.h
@@ -525,5 +525,6 @@ bool xfs_log_check_lsn(struct xfs_mount *, xfs_lsn_t);
 #define XFS_STATS_ADD_OFF(mp, off, val)
 
 typedef unsigned char u8;
+unsigned int hweight8(unsigned int w);
 
 #endif	/* __LIBXFS_INTERNAL_XFS_H__ */
diff --git a/libxfs/util.c b/libxfs/util.c
index f6ce3949d8..584666c2b7 100644
--- a/libxfs/util.c
+++ b/libxfs/util.c
@@ -817,3 +817,10 @@ libxfs_zero_extent(
 	return libxfs_device_zero(xfs_find_bdev_for_inode(ip), sector, size);
 }
 
+unsigned int
+hweight8(unsigned int w)
+{
+	unsigned int res = w - ((w >> 1) & 0x55);
+	res = (res & 0x33) + ((res >> 2) & 0x33);
+	return (res + (res >> 4)) & 0x0F;
+}
diff --git a/libxfs/xfs_attr_leaf.c b/libxfs/xfs_attr_leaf.c
index ead3e71cc9..2e8fb13dd4 100644
--- a/libxfs/xfs_attr_leaf.c
+++ b/libxfs/xfs_attr_leaf.c
@@ -867,6 +867,80 @@ xfs_attr_shortform_allfit(
 	return xfs_attr_shortform_bytesfit(dp, bytes);
 }
 
+/* Verify the consistency of an inline attribute fork. */
+xfs_failaddr_t
+xfs_attr_shortform_verify(
+	struct xfs_inode		*ip)
+{
+	struct xfs_attr_shortform	*sfp;
+	struct xfs_attr_sf_entry	*sfep;
+	struct xfs_attr_sf_entry	*next_sfep;
+	char				*endp;
+	struct xfs_ifork		*ifp;
+	int				i;
+	int				size;
+
+	ASSERT(ip->i_d.di_aformat == XFS_DINODE_FMT_LOCAL);
+	ifp = XFS_IFORK_PTR(ip, XFS_ATTR_FORK);
+	sfp = (struct xfs_attr_shortform *)ifp->if_u1.if_data;
+	size = ifp->if_bytes;
+
+	/*
+	 * Give up if the attribute is way too short.
+	 */
+	if (size < sizeof(struct xfs_attr_sf_hdr))
+		return __this_address;
+
+	endp = (char *)sfp + size;
+
+	/* Check all reported entries */
+	sfep = &sfp->list[0];
+	for (i = 0; i < sfp->hdr.count; i++) {
+		/*
+		 * struct xfs_attr_sf_entry has a variable length.
+		 * Check the fixed-offset parts of the structure are
+		 * within the data buffer.
+		 */
+		if (((char *)sfep + sizeof(*sfep)) >= endp)
+			return __this_address;
+
+		/* Don't allow names with known bad length. */
+		if (sfep->namelen == 0)
+			return __this_address;
+
+		/*
+		 * 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 = XFS_ATTR_SF_NEXTENTRY(sfep);
+		if ((char *)next_sfep > endp)
+			return __this_address;
+
+		/*
+		 * Check for unknown flags.  Short form doesn't support
+		 * the incomplete or local bits, so we can use the namespace
+		 * mask here.
+		 */
+		if (sfep->flags & ~XFS_ATTR_NSP_ONDISK_MASK)
+			return __this_address;
+
+		/*
+		 * Check for invalid namespace combinations.  We only allow
+		 * one namespace flag per xattr, so we can just count the
+		 * bits (i.e. hweight) here.
+		 */
+		if (hweight8(sfep->flags & XFS_ATTR_NSP_ONDISK_MASK) > 1)
+			return __this_address;
+
+		sfep = next_sfep;
+	}
+	if ((void *)sfep != (void *)endp)
+		return __this_address;
+
+	return NULL;
+}
+
 /*
  * Convert a leaf attribute list to shortform attribute list
  */
diff --git a/libxfs/xfs_attr_leaf.h b/libxfs/xfs_attr_leaf.h
index 894124efb4..4da08af5b1 100644
--- a/libxfs/xfs_attr_leaf.h
+++ b/libxfs/xfs_attr_leaf.h
@@ -53,6 +53,7 @@ int	xfs_attr_shortform_to_leaf(struct xfs_da_args *args,
 int	xfs_attr_shortform_remove(struct xfs_da_args *args);
 int	xfs_attr_shortform_allfit(struct xfs_buf *bp, struct xfs_inode *dp);
 int	xfs_attr_shortform_bytesfit(struct xfs_inode *dp, int bytes);
+xfs_failaddr_t xfs_attr_shortform_verify(struct xfs_inode *ip);
 void	xfs_attr_fork_remove(struct xfs_inode *ip, struct xfs_trans *tp);
 
 /*