4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Darrick J. Wong <[email protected]>

commit d5a91baeb6033c3392121e4d5c011cdc08dfa9f7 upstream.

Don't let anybody load an obviously bad btree pointer.  Since the values
come from disk, we must return an error, not just ASSERT.

Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Eric Sandeen <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 fs/xfs/libxfs/xfs_bmap.c  |    5 +----
 fs/xfs/libxfs/xfs_btree.c |    3 ++-
 fs/xfs/libxfs/xfs_btree.h |    2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1278,7 +1278,6 @@ xfs_bmap_read_extents(
        /* REFERENCED */
        xfs_extnum_t            room;   /* number of entries there's room for */
 
-       bno = NULLFSBLOCK;
        mp = ip->i_mount;
        ifp = XFS_IFORK_PTR(ip, whichfork);
        exntf = (whichfork != XFS_DATA_FORK) ? XFS_EXTFMT_NOSTATE :
@@ -1291,9 +1290,7 @@ xfs_bmap_read_extents(
        ASSERT(level > 0);
        pp = XFS_BMAP_BROOT_PTR_ADDR(mp, block, 1, ifp->if_broot_bytes);
        bno = be64_to_cpu(*pp);
-       ASSERT(bno != NULLFSBLOCK);
-       ASSERT(XFS_FSB_TO_AGNO(mp, bno) < mp->m_sb.sb_agcount);
-       ASSERT(XFS_FSB_TO_AGBNO(mp, bno) < mp->m_sb.sb_agblocks);
+
        /*
         * Go down the tree until leaf level is reached, following the first
         * pointer (leftmost) at each level.
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -810,7 +810,8 @@ xfs_btree_read_bufl(
        xfs_daddr_t             d;              /* real disk block address */
        int                     error;
 
-       ASSERT(fsbno != NULLFSBLOCK);
+       if (!XFS_FSB_SANITY_CHECK(mp, fsbno))
+               return -EFSCORRUPTED;
        d = XFS_FSB_TO_DADDR(mp, fsbno);
        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
                                   mp->m_bsize, lock, &bp, ops);
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -491,7 +491,7 @@ static inline int xfs_btree_get_level(st
 #define        XFS_FILBLKS_MAX(a,b)    max_t(xfs_filblks_t, (a), (b))
 
 #define        XFS_FSB_SANITY_CHECK(mp,fsb)    \
-       (XFS_FSB_TO_AGNO(mp, fsb) < mp->m_sb.sb_agcount && \
+       (fsb && XFS_FSB_TO_AGNO(mp, fsb) < mp->m_sb.sb_agcount && \
                XFS_FSB_TO_AGBNO(mp, fsb) < mp->m_sb.sb_agblocks)
 
 /*


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