6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Filipe Manana <fdmanana@xxxxxxxx>
commit c9a75ec45f1111ef530ab186c2a7684d0a0c9245 upstream.
At insert_delayed_ref() if we need to update the action of an existing
ref to BTRFS_DROP_DELAYED_REF, we delete the ref from its ref head's
ref_add_list using list_del(), which leaves the ref's add_list member
not reinitialized, as list_del() sets the next and prev members of the
list to LIST_POISON1 and LIST_POISON2, respectively.
If later we end up calling drop_delayed_ref() against the ref, which can
happen during merging or when destroying delayed refs due to a transaction
abort, we can trigger a crash since at drop_delayed_ref() we call
list_empty() against the ref's add_list, which returns false since
the list was not reinitialized after the list_del() and as a consequence
we call list_del() again at drop_delayed_ref(). This results in an
invalid list access since the next and prev members are set to poison
pointers, resulting in a splat if CONFIG_LIST_HARDENED and
CONFIG_DEBUG_LIST are set or invalid poison pointer dereferences
otherwise.
So fix this by deleting from the list with list_del_init() instead.
Fixes: 1d57ee941692 ("btrfs: improve delayed refs iterations")
CC: stable@xxxxxxxxxxxxxxx # 4.19+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/delayed-ref.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -615,7 +615,7 @@ static bool insert_delayed_ref(struct bt
&href->ref_add_list);
else if (ref->action == BTRFS_DROP_DELAYED_REF) {
ASSERT(!list_empty(&exist->add_list));
- list_del(&exist->add_list);
+ list_del_init(&exist->add_list);
} else {
ASSERT(0);
}
