xfs: verify free block header fields

Perform basic sanity checking of the directory free block header
fields so that we avoid hanging the system on invalid data.

(Granted that just means that now we shutdown on directory write,
but that seems better than hanging...)

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/libxfs/xfs_dir2_node.c b/fs/xfs/libxfs/xfs_dir2_node.c
index 75a557432d0f87fdb4cfa866332c403023d169dc..bbd1238852b3c4f66b76b159847d33e827ced077 100644 (file)
--- a/fs/xfs/libxfs/xfs_dir2_node.c
+++ b/fs/xfs/libxfs/xfs_dir2_node.c
@@ -155,6 +155,42 @@ const struct xfs_buf_ops xfs_dir3_free_buf_ops = {
        .verify_write = xfs_dir3_free_write_verify,
 };
 
+/* Everything ok in the free block header? */
+static bool
+xfs_dir3_free_header_check(
+       struct xfs_inode        *dp,
+       xfs_dablk_t             fbno,
+       struct xfs_buf          *bp)
+{
+       struct xfs_mount        *mp = dp->i_mount;
+       unsigned int            firstdb;
+       int                     maxbests;
+
+       maxbests = dp->d_ops->free_max_bests(mp->m_dir_geo);
+       firstdb = (xfs_dir2_da_to_db(mp->m_dir_geo, fbno) -
+                  xfs_dir2_byte_to_db(mp->m_dir_geo, XFS_DIR2_FREE_OFFSET)) *
+                       maxbests;
+       if (xfs_sb_version_hascrc(&mp->m_sb)) {
+               struct xfs_dir3_free_hdr *hdr3 = bp->b_addr;
+
+               if (be32_to_cpu(hdr3->firstdb) != firstdb)
+                       return false;
+               if (be32_to_cpu(hdr3->nvalid) > maxbests)
+                       return false;
+               if (be32_to_cpu(hdr3->nvalid) < be32_to_cpu(hdr3->nused))
+                       return false;
+       } else {
+               struct xfs_dir2_free_hdr *hdr = bp->b_addr;
+
+               if (be32_to_cpu(hdr->firstdb) != firstdb)
+                       return false;
+               if (be32_to_cpu(hdr->nvalid) > maxbests)
+                       return false;
+               if (be32_to_cpu(hdr->nvalid) < be32_to_cpu(hdr->nused))
+                       return false;
+       }
+       return true;
+}
 
 static int
 __xfs_dir3_free_read(
@@ -168,11 +204,22 @@ __xfs_dir3_free_read(
 
        err = xfs_da_read_buf(tp, dp, fbno, mappedbno, bpp,
                                XFS_DATA_FORK, &xfs_dir3_free_buf_ops);
+       if (err || !*bpp)
+               return err;
+
+       /* Check things that we can't do in the verifier. */
+       if (!xfs_dir3_free_header_check(dp, fbno, *bpp)) {
+               xfs_buf_ioerror(*bpp, -EFSCORRUPTED);
+               xfs_verifier_error(*bpp);
+               xfs_trans_brelse(tp, *bpp);
+               return -EFSCORRUPTED;
+       }
 
        /* try read returns without an error or *bpp if it lands in a hole */
-       if (!err && tp && *bpp)
+       if (tp)
                xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_DIR_FREE_BUF);
-       return err;
+
+       return 0;
 }
 
 int