xfs: check _alloc_read_agf buffer pointer before using

In some circumstances, _alloc_read_agf can return an error code of zero
but also a null AGF buffer pointer.  Check for this and jump out.

Fixes-coverity-id: 1415250
Fixes-coverity-id: 1415320
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

2 files changed, 6 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
index 900ea231f9a3..45b1c3b4e047 100644
--- a/fs/xfs/libxfs/xfs_refcount.c
+++ b/fs/xfs/libxfs/xfs_refcount.c
@@ -1638,6 +1638,10 @@ xfs_refcount_recover_cow_leftovers(
         error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
         if (error)
                 goto out_trans;
+        if (!agbp) {
+                error = -ENOMEM;
+                goto out_trans;
+        }
         cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, NULL);
 
         /* Find all the leftover CoW staging extents. */
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index d9b3d57a1921..f45fbf0db9bb 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -170,6 +170,8 @@ xfs_reflink_find_shared(
         error = xfs_alloc_read_agf(mp, tp, agno, 0, &agbp);
         if (error)
                 return error;
+        if (!agbp)
+                return -ENOMEM;
 
         cur = xfs_refcountbt_init_cursor(mp, tp, agbp, agno, NULL);