NTFS: Fix stupid bug in fs/ntfs/attrib.c::ntfs_external_attr_find() in the

      error handling code path that resulted in a BUG() due to trying to
      unmap an extent mft record when the mapping of it had failed and it
      thus was not mapped.  (Thanks to Ken MacFerrin for the bug report.)
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>

fs/ntfs/ChangeLog

@@ -66,6 +66,10 @@ ToDo/Notes:
 	  buffers belonging to the ntfs record dirty.  This causes the buffers
 	  to become busy and hence they are safe from removal until the page
 	  has been written out.
+	- Fix stupid bug in fs/ntfs/attrib.c::ntfs_external_attr_find() in the
+	  error handling code path that resulted in a BUG() due to trying to
+	  unmap an extent mft record when the mapping of it had failed and it
+	  thus was not mapped.  (Thanks to Ken MacFerrin for the bug report.)
 
 2.1.21 - Fix some races and bugs, rewrite mft write code, add mft allocator.
 

fs/ntfs/attrib.c

@@ -655,7 +655,6 @@ static int ntfs_external_attr_find(const ATTR_TYPE type,
 				ctx->mrec = map_extent_mft_record(base_ni,
 						le64_to_cpu(
 						al_entry->mft_reference), &ni);
-				ctx->ntfs_ino = ni;
 				if (IS_ERR(ctx->mrec)) {
 					ntfs_error(vol->sb, "Failed to map "
 							"extent mft record "
@@ -667,8 +666,11 @@ static int ntfs_external_attr_find(const ATTR_TYPE type,
 					err = PTR_ERR(ctx->mrec);
 					if (err == -ENOENT)
 						err = -EIO;
+					/* Cause @ctx to be sanitized below. */
+					ni = NULL;
 					break;
 				}
+				ctx->ntfs_ino = ni;
 			}
 			ctx->attr = (ATTR_RECORD*)((u8*)ctx->mrec +
 					le16_to_cpu(ctx->mrec->attrs_offset));
@@ -740,7 +742,8 @@ static int ntfs_external_attr_find(const ATTR_TYPE type,
 		err = -EIO;
 	}
 	if (ni != base_ni) {
-		unmap_extent_mft_record(ni);
+		if (ni)
+			unmap_extent_mft_record(ni);
 		ctx->ntfs_ino = base_ni;
 		ctx->mrec = ctx->base_mrec;
 		ctx->attr = ctx->base_attr;