xfs: create structure verifier function for shortform xattrs

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>

diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
index 68c66fa..ae3bccb 100644 (file)
--- a/fs/xfs/libxfs/xfs_attr_leaf.c
+++ b/fs/xfs/libxfs/xfs_attr_leaf.c
@@ -872,6 +872,80 @@ 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/fs/xfs/libxfs/xfs_attr_leaf.h b/fs/xfs/libxfs/xfs_attr_leaf.h
index 894124e..4da08af 100644 (file)
--- a/fs/xfs/libxfs/xfs_attr_leaf.h
+++ b/fs/xfs/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);
 
 /*