[PATCH] bcachefs: Fix NULL ptr dereference in btree_node_iter_and_journal_peek

[Piotr Zalewski]

Add NULL check for key returned from bch2_btree_and_journal_iter_peek in
btree_node_iter_and_journal_peek to avoid NULL ptr dereference in
bch2_bkey_buf_reassemble.

Reported-by: syzbot+005ef9aa519f30d97657@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=005ef9aa519f30d97657
Fixes: 5222a4607cd8 ("bcachefs: BTREE_ITER_WITH_JOURNAL")
Signed-off-by: Piotr Zalewski <pZ010001011111@xxxxxxxxx>
---
 fs/bcachefs/btree_iter.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 0883cf6e1a3e..625167ce191f 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -882,6 +882,8 @@ static noinline int btree_node_iter_and_journal_peek(struct btree_trans *trans,
 	__bch2_btree_and_journal_iter_init_node_iter(trans, &jiter, l->b, l->iter, path->pos);
 
 	k = bch2_btree_and_journal_iter_peek(&jiter);
+	if (!k.k)
+		goto err;
 
 	bch2_bkey_buf_reassemble(out, c, k);
 
@@ -889,6 +891,7 @@ static noinline int btree_node_iter_and_journal_peek(struct btree_trans *trans,
 	    c->opts.btree_node_prefetch)
 		ret = btree_path_prefetch_j(trans, path, &jiter);
 
+err:
 	bch2_btree_and_journal_iter_exit(&jiter);
 	return ret;
 }
-- 
2.47.0