xfs: fix intent use-after-free on abort

When an intent is aborted during it's initial commit through
xfs_defer_trans_abort(), there is a use after free. The current
report is for a RUI  through this path in generic/388:

 Freed by task 6274:
  __kasan_slab_free+0x136/0x180
  kmem_cache_free+0xe7/0x4b0
  xfs_trans_free_items+0x198/0x2e0
  __xfs_trans_commit+0x27f/0xcc0
  xfs_trans_roll+0x17b/0x2a0
  xfs_defer_trans_roll+0x6ad/0xe60
  xfs_defer_finish+0x2a6/0x2140
  xfs_alloc_file_space+0x53a/0xf90
  xfs_file_fallocate+0x5c6/0xac0
  vfs_fallocate+0x2f5/0x930
  ioctl_preallocate+0x1dc/0x320
  do_vfs_ioctl+0xfe4/0x1690

The problem is that the RUI has two active references - one in the
current transaction, and another held by the defer_ops structure
that is passed to the RUD (intent done) so that both the intent and
the intent done structures are freed on commit of the intent done.

Hence during abort, we need to release the intent item, because the
defer_ops reference is released separately via ->abort_intent
callback. Fix all the intent code to do this correctly.

Signed-Off-By: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 20 insertions, 19 deletions

diff --git a/fs/xfs/xfs_refcount_item.c b/fs/xfs/xfs_refcount_item.c
index 7a39f40645f7..15c9393dd7a7 100644
--- a/fs/xfs/xfs_refcount_item.c
+++ b/fs/xfs/xfs_refcount_item.c
@@ -52,6 +52,25 @@ xfs_cui_item_free(
 		kmem_zone_free(xfs_cui_zone, cuip);
 }
 
+/*
+ * Freeing the CUI requires that we remove it from the AIL if it has already
+ * been placed there. However, the CUI may not yet have been placed in the AIL
+ * when called by xfs_cui_release() from CUD processing due to the ordering of
+ * committed vs unpin operations in bulk insert operations. Hence the reference
+ * count to ensure only the last caller frees the CUI.
+ */
+void
+xfs_cui_release(
+	struct xfs_cui_log_item	*cuip)
+{
+	ASSERT(atomic_read(&cuip->cui_refcount) > 0);
+	if (atomic_dec_and_test(&cuip->cui_refcount)) {
+		xfs_trans_ail_remove(&cuip->cui_item, SHUTDOWN_LOG_IO_ERROR);
+		xfs_cui_item_free(cuip);
+	}
+}
+
+
 STATIC void
 xfs_cui_item_size(
 	struct xfs_log_item	*lip,
@@ -141,7 +160,7 @@ xfs_cui_item_unlock(
 	struct xfs_log_item	*lip)
 {
 	if (lip->li_flags & XFS_LI_ABORTED)
-		xfs_cui_item_free(CUI_ITEM(lip));
+		xfs_cui_release(CUI_ITEM(lip));
 }
 
 /*
@@ -211,24 +230,6 @@ xfs_cui_init(
 	return cuip;
 }
 
-/*
- * Freeing the CUI requires that we remove it from the AIL if it has already
- * been placed there. However, the CUI may not yet have been placed in the AIL
- * when called by xfs_cui_release() from CUD processing due to the ordering of
- * committed vs unpin operations in bulk insert operations. Hence the reference
- * count to ensure only the last caller frees the CUI.
- */
-void
-xfs_cui_release(
-	struct xfs_cui_log_item	*cuip)
-{
-	ASSERT(atomic_read(&cuip->cui_refcount) > 0);
-	if (atomic_dec_and_test(&cuip->cui_refcount)) {
-		xfs_trans_ail_remove(&cuip->cui_item, SHUTDOWN_LOG_IO_ERROR);
-		xfs_cui_item_free(cuip);
-	}
-}
-
 static inline struct xfs_cud_log_item *CUD_ITEM(struct xfs_log_item *lip)
 {
 	return container_of(lip, struct xfs_cud_log_item, cud_item);