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btrfs: reinitialize delayed ref list after deleting it from the list

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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: 1d57ee9416 ("btrfs: improve delayed refs iterations")
CC: stable@vger.kernel.org # 4.19+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2024-11-04 12:11:15 +00:00 committed by David Sterba
parent cda7163d4e
commit c9a75ec45f
1 changed files with 1 additions and 1 deletions
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2
fs/btrfs/delayed-ref.c
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@ -649,7 +649,7 @@ static bool insert_delayed_ref(struct btrfs_trans_handle *trans,
&href->ref_add_list); &href->ref_add_list);
else if (ref->action == BTRFS_DROP_DELAYED_REF) { else if (ref->action == BTRFS_DROP_DELAYED_REF) {
ASSERT(!list_empty(&exist->add_list)); ASSERT(!list_empty(&exist->add_list));
list_del(&exist->add_list); list_del_init(&exist->add_list);
} else { } else {
ASSERT(0); ASSERT(0);
} }