xfs: fix potential log item leak

Ever since we added shadown format buffers to the log items, log
items need to handle the item being released with shadow buffers
attached. Due to the fact this requirement was added at the same
time we added new rmap/reflink intents, we missed the cleanup of
those items.

In theory, this means shadow buffers can be leaked in a very small
window when a shutdown is initiated. Testing with KASAN shows this
leak does not happen in practice - we haven't identified a single
leak in several years of shutdown testing since ~v4.8 kernels.

However, the intent whiteout cleanup mechanism results in every
cancelled intent in exactly the same state as this tiny race window
creates and so if intents down clean up shadow buffers on final
release we will leak the shadow buffer for just about every intent
we create.

Hence we start with this patch to close this condition off and
ensure that when whiteouts start to be used we don't leak lots of
memory.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/xfs/xfs_icreate_item.c b/fs/xfs/xfs_icreate_item.c
index 508e184e3b8f..b05314d48176 100644
--- a/fs/xfs/xfs_icreate_item.c
+++ b/fs/xfs/xfs_icreate_item.c
@@ -63,6 +63,7 @@ STATIC void
 xfs_icreate_item_release(
 	struct xfs_log_item	*lip)
 {
+	kmem_free(ICR_ITEM(lip)->ic_item.li_lv_shadow);
 	kmem_cache_free(xfs_icreate_cache, ICR_ITEM(lip));
 }